Physics Name Period Date _

C-5 Vocabulary - Newton s Laws

1. Force

2. Inertia

3. Law of inertia

4. Newton s first law

5. Net force

6. Dynamics

7. Equilibrium

8. Statics

9. Newton’s second law

10. Locomotion

11. newton (N)

12. Action

13. Reaction

14. Newton s third law

Name Hour Ch.5 Guided ReadingPhysics

1. Who was Sir Isaac ewton?

List Newton s accomplishments before the age of 30.

2. In physics, explain what a force is and what it has the ability to do.

Name several ways in which forces can be created.

Can a change in motion occur if no force is applied? If so, provide an exam le.

3. Describe Newton's first law and how inertia affects the motion of an object.

How are mass and inertia related?

What is the origin of the word inertia? How does the word's origin help to describe its meaning?

4. Here are three systems in a car designed to overcome the law of inertia. Briefly describe each.Engine -

Brakes -

Steering -

5. What do seatbelts, airbags, and cup holders have to do with Newton's first law?

6. Describe Newton's secon law of motion.

What is the for ula associated with Newton's second law? Label the variables.

7. What are newtons (N) and pounds (lbs) used to measure? Compare each of these units to the kilogram.

What conversion factor should be used when converting from pounds to newtons?Correctly use this factor to convert 150 pounds to newtons. Show your work.

8. Use Newton s second law to explain the relationship seen bet een mass, length, and time in these units: kg-m/sec2.

What do these units have to do with newtons?

9. What is meant by the phrase net force?

How do you calculate net force acting on an object? Provide an example.

10. Use the a pro riate formula to perform each of the following calculations concerning Newton's second law.

a. A car rolls down a ramp. Using a spring scale, you measure a net force of 3.5 newtons pulling the car down. The

car has a mass of 0.75 kg. Calculate the acceleration of the cart.

. A force of 12 newtons is applied in order to accelerate a ball at a rate of 4 m/sec2. What is the mass of the ball?

c. What forc ust have been applied to a celerate a 24-kg bo ling ball at a rat of 6 /sec2?

11. What units MUST be used in order for the equations in Newton's second law (in the previous question) to work?

12. What does the word dynamics mean in physics class?

Explain why we use positive and negative numbers in dynamics roblems, in general, what are the rules?

13. How do we determine whether an objector condition is in equilibrium? Provide an example.

What is a static problem and how might engineers use them?

1 escribe Newton's third law.

15. Draw a diagram showing an action-reaction pair of forces.

16. Describe the serious problem astronauts have when mo ing in space.

How does the phrase forces aiways come in pairs relate to this problem?

17. Explain ho forces work in pairs for objects at rest.

18. Which way do the forces in an action-reaction pair always point?

19. In general the first and second laws apply to single objects. How does the third law differ?

20. What steps are necessary to determine the reaction force when given an action force?

21. What is locomotion?

Explain how locomotion is achieved in the water or in the air using Newton s third law.

22. What is biomechanics?

List and explain at least two examples of when biomechanics would be used.

Name: Cl ss: Date: ID: A

Ch pter 05 Pretest

M ltiple ChoiceIdentify the choice that best completes the statement or answers the question.

1. The inertia of an object comes from its:a. acceleration.

b. mass.

c. speed

d. force.

2. hat action must be taken to change the motion of an object?a. Mass must be dded to the object.b. "Weight ust be added to the objectc. Friction must be eliminated.d. Force must be applied to the object

3. T e acceleration ofan object is:a. equal to its weight.b. equal to its mass divided by t e force acting on the object.c. equal to the force acting on the object divided by t e mass of the object.d. equal to the force cting on an object multiplied by the mass of the object

. hich ofl e following situ tions MUST have a net force?a. An object acceler tes from 1 m/s2 to 2 m/s2.b. An object is at rest with zero speed.c. An object is moving with a constant speed of 2 m/s.d. A obj ect has a mass of 1 kilogram.

5. A basketball player with a mass of 70 kilograms jumps upward by pushing a ainst the floor with his feet witha force of 1,200 newtons. "Which is the best explanation for hy the basketball layer moves upward?a. The player s feet are connected to the r st of his bod and distribute the 1,200-ne ton

force over the whole body.b. The floor ushes back upward on the player with a force of 1,200 ne tons, which lifts

die player off the grou d.c. The 1,200-newton force is equal to he force of gravity holding the player down.

. The player s weight is reduced by the 1,200-newto force.

I

Newton s Laws

Pre-Conceptions

Students typically ha e many pre-conceived notions regarding concepts in Physics. It h s always provenuseful to brin these ideas to the forefront of your mind and to make a effort to e alu te theircorrectness. The followin statem nts per ai in one way or anot er to commo notions re ardin ce ral concepts of his unit Identify e ch statement as bein eit er true (T) or false (F)-

Force and Mo ion - What Do You Believe?

The followi g stateme ts ertain in one way or another to commo otions re ardin force and motion.Ide tify each s ateme t as bei either true (T) ox f lse (F).

TorF? Statement1. A force is required to keep an object moving in a ive direction.

2. An upward movin objec must be experiencin (or at least usually does experie ce)a upward force.

3. A i htward ovin o ject must e experiencin (or at le st usuall does experie ce)a ri ht ard force.

4. A ball is movin upwards and ri ht rds towards its peak. The ball experiences aforce t at is directed upwards and ri h wards.

5. If a erson throws a ball with is hand, the t e force of the hand pon the ball isexperienced the ball for at least a little while after the ball leaves the hand.

6. A can onball is shot from a ca no at a ver hi h speed. The force of t e explosio will e e perienced by the ca onball for sever l seconds (or a least a little hile).

7. If an objec is at rest, then there are o forces act n upon the object.

/

Mass and Weight - What Do You Believe?

The following statements per ain in o e way or another to co mo notions re ardi g ass a d wei tIdentify each s tement as bein eit er true (T) or false (F).

T or F? Statement1. Objects do NOT ei h anyt in en placed i a vacuum.

2. All o jects ei h e sa e amo t when placed i a vacuu , re ardless of theirass.

3. An object wei hs less on t e oon tha it oes on t e Earth.

4. e mass of an object on the moon is the same as its mass on the-E rth.

5. A hig -speed objec (s y, mo in at 200 mi/hr) ill wei h less than the same objec when at rest

6. A i h-speed object (sa , movin at 200 mi/hr) ill possess easurably ore assthan t e sa e object hen t rest

7. Wei ht is measured i potmds; ass is measured in Ne tons.

8. A free-fallin object still as w i t

9. Weig t is t e result of air pressure exerted po an objec

(

Newton's Laws Name:

I ertia and Mass

. • *•

MOP Co nection: Newton s aws: sublevel 1

1. Inertia is

2. The amount of i ertia possessed by an object is dependent solely upo its .

3. Two ricks are resting o edge of the lab table. Shirle Sheshort stands o . er toes a d spots t two bricks. Sh ac uires a intense desire to no whi of t e two ricks are most ssive. Sinc Shirley is vertically challenged/- s e is u able to re ch ig enoug a d lift t e bricks; she ca however reach hi h enou to gi e the bricks a p sh. Discuss how he process of shin the bricks

ill allow Shirley to deter i e which of the t o bricks is ost massive. What difference willS irley observe and how ca this observatio le d to th ecessa conclusion?

L Would Shirle Shes ort be a le to co d ct this same study if she was on s ceshi in a locatio inspace far from the influence of significant gr itational forces? E lain your answer.

5. If moose were c asin ou through t e woods,- its enormous mass would h very t eateni . Butif you zigza ed, then its great mass w uld be to your ad anta e. Explai hy.

6. Inertia ca best be described as .a. t e forc hich keeps movi objects mo i a stationar objects at rest. the illingn ss of an object to eventuall lose i s otio

t e force whic causes all objects to stopd. t e te dency of object to esist chan e a d eep doin tever its doing

7. Mass and velocity values for a ariety of ob ects are listed elow. R nk the objects from smallest toreates inertia. < < <

=2Ws • =0 n s v=4Ws v=3t ?

m=IB kg to=20 kg •m=5 g •m=8kg

SgeciA CSy&dB CSgectC GfcjectB

Hewl&n s laws IMsMsShow ail work on a separate sheet of paper.

1. A little boy pushes a wagon with his dog in it. The mass of the dog and wagon togetheris 45 kg. The wagon accelerates at 0.85 m/s2. What force is the boy pulling with?

2. A 1650 kg car accelerates at a ate of 4.0 m/s2. How much force is the car's engineproducing?

3. A 68 kg runner exerts a force of 59 N. What is the acceleration of the runner?4. A crate is dragged across an ice covered la e. The box accele ates at 0.08 m/s2 and

is pulled by a 47 N force. What is the mass of the box?5. 3 women push a stalled car. Each woman pushes with a 425 N force. What is the

mass of the car if the car accelerates at 0.85 m/s2?6. A tennis ball, 0.314 kg, is accelerated at a rate of 164 m/s2 when hit by a professional

tennis player. What force does the player's tennis racket exert on the ball?7. In an airplane crash a woman is holding an 8.18 kg, 18 pound, baby. In the crash t e

woman experiences a horizontal de-acceleration of 88.2 m/s2. How many g's is thisde-acceleration? How much force must the woman exert to hold the baby in place?

8. When an F-14 airplane takes-off an aircraft carrier it is literally catapulted off the flightdeck. The plane s final speed at take-off Is 68.2 m/s. The F-14 starts from rest. Theplane acceler tes in 2 seconds and has a mass of 29,545 kg. What is the total forcet at gets the F-14 in the air?

9. A sports car accelerates from 0 to 60 mp , 27 m/s, in 6.3 secon s. The car exerts aforce of 4106 N. What is the mass of the car?

ID. A sled is pushed along an ice covered lake. It has some initial velocity before comingto a rest in 15 m. It took 23 seconds before the sled and rider come to a rest. If theri er and sled have a combined mass of 52.5 kg, what is the magnitude and directionof the stopping force? What do "we call the stopping force?

It. A car is pulled with a force of 10,000 N. The car s mass is 1267 kg. But, the car covers394.6 m in 15 seconds.ta} What is expected acceleration of the car from the 10,000 N force?El!) What is the actual acceleration of the car from the observed data of x and t?fc3 What is the difference in accelerations?[fH What force caused this difference in acceleration?[&) What is the magnitude and direction of the force that caused the difference in

acceleration?12. 12. A little car has a aximum acceleration of 2.57 m/s2. What is t e new maximum

acceleration of the little car If it tows another car that has the same mass?13. 13. A boy can accelerate at 1.00 m/s2 over a short distance. If the boy were to take

an energy pill and suddenly have the ability to accelerate at 5.6 m/s2, then how wouldhis new energy-pill-force compare to his earlier force? If the boy's earlier force was 45N, what is the size of his energy-pill-force?

1 . 14. A cartoon plane with four engines can accelerate at 8.9 m/s2 when one engine isrunning. What is the acceleration of the plane if all four engines are running and eachproduces the same force?

Name:

Skill Sheet 5.2 Newtor s Secon Law

As you wor through t e roblems here, you will develop your understanding of Newton s second law ofmotion and how it relates to Newton s first law of motion The second la states that the acceleratio of anobject is directly proportion l to the force acting on the object and indirectly proportional to the mass of theobject

1. Newton s first law of motionNewton's first law of motion (the law of inertia) states that the motion of an object will continue until a outsideforce changes it. T e amount of force needed to c ange t e motion of an object de ends o the a ou t ofinertia the object has. The inertia of an object is related to its ass. You need more force to move or stop ano ject with a lot of mass or inertia tha you need for an object with less mass or i ertia.

In Newton s second law, the acceleration of a object is directly related to the force on it, and inversely relatedto the mass of the object. This is show in t e formula below:

acceleration =force

mass

Units for acceleration are m/s2. U its for force are newtons (N). One newton is e uivale t to 1 kg-m/s2. Unitsfor mass are ilograms (kg). The equation for acceleratio illustrates t at acceleration is equal to the ratio offorce to mass. This means t at the force on an object causes it to accelerate, but the object s mass is a meas reof how m ch it will resist acceleration.

Three ways to write Newton’s second law of motion

In t e for ula for t e secon law of motion, acceleration equals force di ided by mass. What does mass equal?What does force equal? Rearrange t e equation to solve for mass. Then rearrange t e e uation to solve forforce.

What do you want to know? What do you know7 The formula you will use

acceleration {a) force (F) and mass (m). . force

acceleration = mass

mass (m) acceleration (a) and force (F)

force {F) acceleration (a) a d mass (m)

3. Solving problems using ewton’s second law

Solve t e follo ing problems usi g ewton’s seco d la . The first two problems are done for you.

1. Ho much force is needed to accelerate a truck with a mass of 2,000 kilograms at a rate of 3 /sec ?

3 in = xa = 2,000kgx = 6,000 kg~ = 6,000

s s

Skill Sheet Newton's Second Law

2. What is the mass of an object that requires 15 N to accelerate it at a rate of 1.5 m/sec ?

15 kg-m

m F 15 Na 1.5 m 1.5 m

= 10 kg

3. hat is the rate of acceleration of a 2,000.-kilogram truck if a force of 4,200 N is used to make it startmoving forward?

4. What is the acceleration of a 0.30 kilogram ball that is hit with a force of 25 N?

5. How much force is needed to accelerate a 68 kilogram-skier at a rate of 1.2 m/sec ?

o. hat is the mass of an object that requires a force of 30 N to accelerate at a rate of 5 m/sec2?

7. What is the force on a 1,000 kilogram-elevator that is falling freely under the acceleration of gravity only?

8. What is the mass of an object that needs a force of 4,500 N to accelerate it at a rate of 5 /sec2?

9. What is the acceleration of a 6.4 kilogram bowling ball if a force of 12 N is applied to it?

Physics Wcirfcskffltt: Newton's Srd Law

Mutlipfe ChoiceChoose the best answer toeach question. Writs the letter for that answer to the left of the questionnUtnbar,

Whenever an object rts a force on another object, the second obj'ect e erts a force of thesame magnitude, but in the opposite direction to tha of the first object.

a) Always trueb) Sometimes truec) lwa s false

A high school s udent hits a nail with a hammer. During the collision, there is a forceI

a) on t e ammer but not on the nail.b) on the nail b t not on the ham er.c) on the nail and also on t e ham er.

A woman weig ing 500 N sits on the floor. She exe ts a force on the floor of

a) 1000 N.b) 500 N.c) 250 N.d) SO -e) 5 N.

As a 500 N woman sits on t e floor, the floor exerts a force on er of

a) 1000 N.b) SOON.c) 250 N.d) SON.e) 5 N.

Forces alwa s occur

b) by themselves.b) as sin le qu ntities.c) In pairs.d) to triplets.

\

Page f

An archer s oots an arrow. Conside t e action force to be the bo string against the arrow.The reaction to this fo ce Is the

a) weight of t e arro .b) air resistance against the bow,c) friction of the ground against the archer's feet.d) grip of the arc er's and on the bow. ve) arrow's push against the bowstring.

A player catches a ball. Consi er the action force to be the Impact of the ball against theplayer s glove. What Is the reaction to this force?

a) T e player s grip on he gloveb) The force the glove e erts on the ballc) Friction of t e ground against the pla er s shoesd) The uscular effort In the player s armse) none of the above

A player hits a ball with a bat. The acllon force is the impact of the bat against he ball. Whatis the reaction to this force?

a) ir resistance on t e ballb) The weight of t e ballc) The force of t e ball against the bat) The grip of the player’s han ag inst the ball

e) none of the above

As a ball falls, the action force is the pull of the eart s mass on t e ball. What is t e reactionto this force?

a) Air resistance acting against the halfb) The acceleration of the balfc) The pull of the ball s mass on he ear hd) Nonexistent in this casea) none of t e abo e

A person is attracte towards the center of Ihe earth by a 500-N gravitational tores. The forcewith hich t e eart is attracted towar i e person is

a) very ver small.b) ve y very large.c) SOON.

cs Wo 3t: Newton's 3rd La

An unfortunate bug splatters against the windshield of a moving car. Compared to the force*of the car on the bug, the force of the bug on the car Is

a) larger.b) smaller.c) the same.d) Need more infor ation to eay

12. An unfortunate bug splatters against the windshield of a oving car. Compared to thedeceleration of t e car, t e deceleration of the bug is

a) larger. ftb) smaller. ' ) the sa e.

J3. ff a horse ulls on a wagon at rest, the a on pulls back equally as much on the horse. Willf e wagon be set Into motion?

a) No, because the forces cancel each other.b) Yes; because th re is a net forc acting on the wagon,c} Yes, because th re Is a time delay between action and reaction,d) Yes Th horse's pull an the wagon is larger than he wagon s pull on the orse.

4, Mack truck and a Volkswagen traveling at the same speed have a ead-on collision. Thevehicle to un ergo the r a er change In velocit wifi be t e

f

a) Volkswagen.b) Mack truck.c) Both the same

15. Two people pull on a rope In a tug-of- ar. Each pulls with 400 N of force. W at Is the tensionin the rape?

a) Zerob) 400 Nc) BOONd) BOO Ns} none of the above

16. According to Ne ton s third law, If you push gently on something, It will push

a) gently on you.b) gently on something else.c) on so ethin only under the right conditions.d) on you only if ou aren t oving.

Page 3

Physics Wor s eet: Newton's 3rd Law

,17. The arth pulls on t e oon, and similarl t e oon pulls on he earth. This is evidence t atthe

a) earth and moon are si ply pulling on each other.b) earth’s an moon s pulls co prise an action-reaction pair.c) both a and bd) neither a or

18. Nellie Newton olds an apple in her han . If action is the earth pulling on the apple, t enreaction is

a) her hand pushing up on the apple.b) her hand provi ing a normal fo ce on the apple,c) bot a and bd) neither a or b

,13. Bronco fhe sk iver fails toward the earth. The attraction of the earth on Bronco ulls imdown. T e reaction to this force Is

a) Bronco finally pushing against the earth's surface.b) the earth's surface finally pushing against Bronco.c) Bronco pulling u on t e earth.d) neither a, b or c

20. A force is e erte on the tires of a car to accelerate the car along the road. The force isexerte by the

a) engine.b) tires.c) air.d) road.

21, A rocket Is able to accelerate in the acuum of space when It fires its engines. The force thatpropels t e roc et is the force

a) by the exhaust gases on the roc et.b) of the rocket on the exhaust gases.c) neither a or b

22. wo people, one having twice the mass of the other, play tug-of-war ith a 12 meter rope onfrictionless ice. After a brief time, the e t. T e heavier erson slides a distance of

a) 3 .b) m.c) 5 m;d) 0 m.

Page 4

Name:

Newton s Laws: Force and Motion

1. Four forces are acting on t e hot air balloon as shown in the diagram below.

What is th size and direction of the net force acting on the balloon?

2. Two dogs, Gizmo and Jackson, are pulli g on ropes attached to a metal stake in t e ground. W en they pullin t e same direction the net force is 225 ne tons. W en they pull in opposite directions, the net force is175 ne tons in ackson s di ection. W at force does each dog exert?

3. The sketc es below co ld represent the relations ip bet een the force, mass and acceleration of variousobjects.

2/?/

7///

7

Vft

ss I

Si

s\

12 3 4

I dicate which graph would best represent the relationship between the variables i each example belo .

Acceleration as a fu ctio of mass when a co stant force is a lied

b. Acceleration as a fu ction of force hen applied to a constant mass

4. A 2,000-kilogram object sits motionless while a 2.0-kilogram object moves at 50 m/s. Which object hasmore i ertia?

Skin Sheet Newton s Laws: Force an Mot on

5. Jen y whirls a ball attached to a string at constant speed in a horizontal path. A target is located near thepath as show i the diagram below.

At which point along the ball’s path should Jenny release the string if she w nts to hit the target with theball?

6. The occupants of the car represented in the diagram below are traveling in a circle at constant speed.

In which direction does their inertia tend to cause them to travel?

7._ Joaquin, a 50-kilo r m boy, is rolling on a mountain board at 4.5 m/s on a level, frictionless surface.Calculate the force re uired to keep the board moving at this s eed.

8. The iagram below shows a 4.0 kilo ram object accelerating at 10. meters er second2 on a rough,horizontal, wooden surface. (Forces NOT drawn to scale)

Newton's Laws Name;

Balanced vs. Unbalanced Forces

t

Review: An object at rest..

An obj'ect in motion..

unless ..

1. The amount of force required to keep a 6-kg ob ect moving with a constant eloaty of 2 m/s is N.a. 0.333 b. 2 c 3 d. 6 e. 12f. ... nonsense! A force is NOT required to keep a objec in otion.

2 Renatta Oyle is havi g car troubles. She is notorious for the trail of oil dro s th t she leaves on thestreets of Gle view Observe the following oil traces and indicate whether Re atta s car is bei gacted u on by n un alanced force. Give a reason for your a swers.

3 Each o e of the dot diagrams i question #2 ca be matched to a force diagra below. The forcedia rams de ict the i dividual forces actin upon the c r by a vector arrow. h arrow directionrepres ts the direction of t e force. T e arrow le gth represe ts the stren t of the force. Matc the dot dia ra s from #2 to a force diagram; not every force dia r m needs to be matched.

Dot Diagrain(s): Dot Diagram(s):

If the et force actin upo an object is 0 N, the the object MUST . Circle one answer.. be ovin b. be accelerati c. be at rest

d. be movi with a constant speed i the s me direction e. ei her c or d.

4.

Newton's aws

5 These graphs describe the motion of Carson Busses at various times during his tnp to school.Indicate whether Carsoris vehicle is bein acted upon by a unbalanced force. Give a reason interms of a descri ion of what the car is doin (speedin up, slo ing down, or constant elodty).

Velocity Velocity j--

V locit

Time Time Ti e

Unbalanced Force?Yes or o?

Reason/Description:

Unbalanced Force?Yes or No?

Reason/Description:

Unbalanced Force?Yes or No?

Reason/Description:

6.

7.

A free-body dia rams show all the i dividual forces ac in upon an object. The net force is thevector sum of all these forces (£F). Determine the net force and state if there is an acceleration.

a b. c.

F£r t=10N 1rraJJI„=*N

111FgOT=20N

Accel'n? Yes or No Accel n? Yes or No Accel n? Yes or No

During an in-dass discussion, A na Litical suggests to her lab partner that the dot dia ram for themotion of the object in #6b could be

Anna's partner objects, ar uing t at the object in #6b could not have any horizontal motion if thereare only vertical forces actin pon it Who is ri ht? Ex lai .

8. Durin an in-dass discussion, Aaron in asser s t at the object in #6a must be oving to the leftsince the only horizontal force actin upon it is a "left-ward" force. Is he ri ht? Explain.

9. The diagra s below depict the magnitude and direction of the individual forces actin upon anobject Which objects could be movin to the ri h ? Cir e all h t p ly.

ffl18¥

Name:

Period: Isaac Newton s 3 La s of MotionCh.3:l

Sir Isaac Newton (1642-1727) was an English physicist and mathematician. Before the age of 30 hefor ulated the la s of motion and invented calculus Muc of our modem science is based on Newton s

Law One - Law of InertiaAn object at rest ill stay at r st unless

acted on by an unbalance force.An object in motion will stay

in motion unless acted u on byn unbalanced force.

ORThings keep moving or stay at rest,unless a net force cts upon them.

Newton s La s of Motion

Law Two - F = maThe acceleration of an object is pro or¬

tional to the force acting on itand inversely proportional to its mass.

ORForce causes acceleration,

while m ss resists acceleration

Law Three -Law of Equal nd Opposite Forces.Whenever one object exer s a force on

another object, the second e ert anequal and opposite force on the first

ORFor every action there is an equal

and opposite reaction.

Inertia

Inertia is the property ofan object that resistschange of motion.

Moving objects have inertia:they want to keep moving;

stopped objects have inertia:they want to stay at rest.

More mass - more inerti !

Something th t is harderto push has more inertia!

Force

More mass,more inertia

Net Force

A force is any action that can change or cause motion.A fo ce is any push or puli.

e use Newtons (N) to measure force.

Net force is the sum of all the forces and has direction.(Be sure to make right positive and left negative.)

Less mass,

less inertia

An objectwill move in the

direction of the net(or unbalanced)

force.

-400N +200N

Net Force = + 200 N - 400 N = - 200 N (lef )

Newton s Second La

Force _(m Newtons)

F = maMass(m kg)

Acceleration(in m/sec2)

Force equals m ss times acceleration.

F = ma tells us:

For the sam acceleration,more mass

requires more force.

For the same mass,more acceleration

requires more force.

Newton s 2nd Law tells us that whenyou accelerate (stomp on the gas) ordeceler te quic ly (brake fast) you use

ore force and wear out engine partsand brakes f ster.

Ex. How big a force does it take to give a50 kg object n acceleration of 40 m/s2.

Variables: Solve:40 m/s2=a F = ma50 kg = mF= ?

F = 50( 0)F = 50 x 40

Equation:F = ma

F = 2000N

Ex. If a 50 N force pulls on a10 kg object, how muchacceleration will occur?

Variables: Solve:50N=F F = ma10 kg = m 50 = 10aa= ?

50 _ Xa

Equation: 10 F = ma a = 5m/s2

Ex. A force of 49 N causes a 7 /s1acceleration Find the mass of the

object it was pulling.

Variables: Sol e:49N = F F = ma7 m/s2= a 49 = m7m= ? 49 m\

Equation: 7 \F = ma m = 7 kg

Name:

Period:

Ch.3:l

1. F-.

2. m =

3. a= .

4. v= .

5. D =

6-p- .

125 kilograms

23 kgm/s

3 m/s2

29 meters/sec

228 meters

6 newtons

1. Inertia A. An action that can c uses motion.

2. Mass B. Force pulling all object toward eachother.

3. GravityC. The amount of matter in an object

4. Net force D. Total of all of the forces on an object

5. Force E. Ability of n object to resist change ofmotion.

Number these from least (1) to most (5) inertia.

A baseball A smallcar

A truck A feather A largetrain

Number these from least (1) to most (5) omentum.

Fast car Parked Slow car Fast Fasttruck baseball feather

Which of Newto s Three Laws Applies?Law 1,2, or 3?

When you put a book on a table the table ushes on the book.

A person is pushed forward into their seatbelt when a carstops.

A larger car takes more force to move.

A erson leans on a wall and the wall pushes back.

A brick sits on a table until you push on it

Underst nding Net Force

SON

Which way willit acceler te?

M

6N

15 N

M

M

25 N

8 N

15 N

A sled is bein pulled to the left by 5 dogs, each dog pulling with6 Newtons of force. Fmd the net force.

If a person pulls on a cart to the right ith force of 10 N and asecond person pulls to the left with a force of 3 N, what is the netforce (+ direction) on the cart?

A 2 N and 6 N force ull on an object to the right and a 4 Nforce pulls to the left a 0.5 kg object. What is the net force onthe object?

A 20 kg bike accelerates at 10 m/s2. With what force as theperson pedaling?

If a person is pushing a cart with a force of 40 Newtons and itaccelerates at 0.5 m/s2, what is the mass of the cart?

What is the acceleration of a 3 kg rock that is thrown with a forceof 18 N?

Physics Name Period Date

KElfiroiS LAlfS - RSfetfMATCHIN :

Terms:velocity vector quantitysupport force speedNewton s 1st Law Newtonnet force inertiaforce equilibrium rule

1. The property of things to remain at rest if at rest, or in motion if in motion.2. The distance travelled per time3. The speed of an object in a particular direction4. A quantity that specifies direction as well as magnitude5. Every object continues in a state of rest, or in a state of motion in a straight line at a

constant speed, unless it is compelled to change that state by forces exerted upon it.6. A push or pull.7. The combination of ail forces that act on an object.8. The scientific unit of force.9. ZF = 010. The force that supports an object against gravity.

RE IE QUESTIONS: Think - Pair - share

Newton’s 1st Law - the Law of Inertia1. Who was the first to discover the concept of inertia - Galileo or Newton?2. What is the tendency of a moving object when no forces act on it?

Net Force - The Combination of all Forces that act on an object.3. When only a pair of equal and opposite forces act on an object, what is the net forceacting on it?4. WeVe learned that velocity is a vector quantity. Is force also vector?

Equilibrium for Objects at Rest5. What is the name given to the force that occurs in a rope when both ends are pulled inopposite directions?6. How much tension is there in a rope that holds a 20-N bag of apples at rest?7. What does ZF = 0 mean?

The Support Force - Why we don t fall through the floor8. Why is the support force on an object ofte called the normal force ?9. When you weigh yourself, are you actually reading the support force acting on you, orare you really reading your weight?

Equilibrium for Moving Objects10. Give an example of something moving when a net force of zero acts on it.11. If we push a crate at a constant velocity, how o we know how much friction acts onthe crate compared to the pushing force?

The Earth Moves Around the Sun12. If you are in a smooth-riding bus that is going at 50 km/hr and you flip a coin vertically,what is the horizontal velocity of the coin in midair?

II

Physics Name Period Date

CONCEPTUAL PRACTICE PROBLEMS: Now it the time for you personally to shine. More useof your brain, notes thoughts,.... Need I go on????

1. Galileo found that a bail rolling down one incline will pick up enough speed to roll upanother. How high will it roll compared to its initial height?

2. Correct your friend who says, The race car driver rounded the curve at a constantvelocity of 100 km/hr.

3. If the speedometer of a car reads a constant speed of 50 k /hr, can you say with certaintythat you have constant velocity? Why or Why not?

4. If a huge bear were chasing you, its enormous mass would be very threatening. But if youran in a zigzag pattern, the bear s mass would be to your advantage. Why?

5. A space probe may be carried by a rocket into outer space. What eeps the probe goingafter the rocket no longer pushes it?

6. Consider a ball at rest in the middle of a toy wagon. When the wagon is pulled forward,the ball rolls against the back of the wagon. Interpret this observation in terms of NewtonsLaws.

7. Why do you lurch forward in a bus that suddenly slows? Why do you lurch backwardswhen it picks up speed? What law applies here?

8. Push a shopping cart and it moves. When you stop pushing, it comes to rest Does thisviolate Newton's Law of Inertia? Defend your answer.

9. When a car moves along the highway at a constant velocity, the net force on it is zero.Why then, do you continue to run your engine?

10. Roll a bowling ball down a lane and you ll find it moves slightly slower with time. Doesthis violate Newton’s Law of Inertia? Defend your answer.

11. Consider a pair offerees, one having a magnitude of 20 N and the other with 12 N. Whatmaximum net force is possible with these t o forces? What is the minimum net force?

12. Can an object be in mechanical equilibrium when there is only a single force acting on it?Explain your answer.

Edited-a[m2017

Principles of Physics

Name Hour

5.1 The First Law: Force and Inertia

Key Question: How does the first law apply to objects at rest and in motion?>

What is a force?

>Large Large inertia Change in

motion

>1 m/s2

>

Which force will actually move the box?

> >

What is inertia? What is a contact force?

> What is a non-contact force?

Smallforce

Small Change ininertia motion

-1 m/s2

List several common forces and their descriptions.

>

Principles of Physics

How do these systems in a car o ercome the law of inertia ?

The engine

The break system

>

The steering wheel and steering system

5.2 The Second Law: Force, Mass, and Acceleration

Key Question: What is the relationship between force, mass, and acceleration?>

Look closely at the following two slides. In terms of the 2nd law, explain what each demonstrates...

Principles of Physics

This is the equation that represents Newton s Second Law..

Force: (simple definition)

Force: (deeper definition)

Label the variables...

In the English system, the unit offeree, the

was originally defined by .

-i The metric definition of force depends on the

per

One pound (ib) is the force exerted bygravity on a mass of 0,454 kg.

0.454 kg

Gravity

We call the unit of force the newton in the metric system.

What is a newton exactly equal to?

Net Force (F)

-i The force F that appears in t e second law is the

There are often acting on the

results from the combined action of _

-1 When used this way, the word net means .

, object.

that act on an object.

Force (English-to-metric conversions).

Principles of Physics

pound = about newtons.

How do you solve problems that have multiple forces?

Fill in the three forms

of Newtons 2nd Law

Use if you ' .ant U nr.d jnd you Itno.s

1

The acceleration (a) The net force (F) and themass (m)

1

The net force (F) The acceleration (a) and themass (m)

The mass (m) The acceleration (a) and thenet force (F)

Calculating acceleration: A cart rolls down a ramp. Using a spring scale, you measure a net force of 2 N

pulling the car down. The cart has a mass of 500 grams (0.5 kg). Calculate the acceleration of the cart.

Show all work! ,m = 0.5 kg

Define dynamics.

i Speed when the

is in the direction as the

-i Speed when the

is in the direction as the

Why do we use positive and negative numbers?Principles of Physics

When might the choice be to use positive numbers for force, velocity and acceleration?

Calculating acceleration and determining direction:

Three people are pulling on a wagon applying forces

of 100 N, 150 N, and 200 N (refer to the diagram tothe right). Determine the acceleration and the

direction the wagon moves. The wagon has a mass of

25 kilograms. Show all work!

Finding force from acceleration

i Wherever there is acceleration there must also be

Any change in the motion of an object results from

-i Therefore,

Calculating force: A tennis ball contacts the racquet for much less than one second. High-speed

photographs show that the speed of the ball changes from -30 to +30 m/sec in 0.006 seconds. If the

mass of the ball is 0.2 kg, how much force is applied by the racquet? Show all work!

/r~~~ 1 \

m/s IV I

/ ?p \

fLJi £; 1A s? f

m/s IV 1 J

Weight is

Weight vs. Mass:

How do you calc Weight?

Equilibrium

What is equilibrium?

Principles of Physics

What happens to forces in equilibrium?

Why are objects that are standing still (at rest) considered to be in equilibrium?

Why are objects traveling at constant speed and direction considered to be in equilibriu ?

What is a static problem?

i

Calculating force: A woman is holding two dogs on a

leash. If each dog pulls with a force of 80 newtons,

how much force does the woman have to exert to

keep the dogs from moving?

5.3 Newton s Third Law: Action and Reaction

Bookon table

Tabison book

Tabl on floorfloor

on table

Flooron wall

Wallon floor

Wallon Earth

Earthon all

The 3rd law discusses pairs of objects & the interactions between them.

State Newton s 3rd Law...

Explain how this diagram demonstrates the fact that forces act in pairs.

t

What are action and reaction pairs?

How can you determine one from the other?

ACTIONYou pushing jon ground

Princ ples of Physics

The 3rd law states that for every action force there has to be a reaction force that is equal in strength and

opposite in direction. Do action-reaction forces act on different objects or on the same object?

Explain!

Why don t the forces in action-reaction situations cancel each other out?

Calculating Force: Three people are each applying 250 newtons offeree to try to move a hea y cart. The

people are standing on a rug. Someone nearby notices that the rug is slipping. How much force must be

applied to the rug to keep it from slipping?Show ail work!

3 people .1250 N eac b

Sketch the action and reaction forces acting between the

people and the cart and between the people and the rug. -i

what is Locomotion?

To get around, what does any animal or machine that moves depends on?

Explain walking in terms of Newton's 3rd Law.

Sketch the action and reaction forces acting

between the person walking and the floor, -i

Action Reaction Forces:

List the Force pairs: and helicopter up

BSads on air molecuSespushes air molecules down

Physics Name Lab Period Date

Newton s Second Law

Background:Newtons second law of motion states that acceleration is directly proportional to the force usedand inversely proportional to the mass the force acts on. This iab pro ides an opportunity to testan verify that law.

Procedure:1. Level the dynamics track by setting the cart on the track and checking to see which way it rolls.Adjust the level, if necessary, until a cart placed at rest on the track does not move.

2. For each trial, use the same procedure to run the cart. Cock the spring plunger to the desiredposition. Place the end of the cart at rest against the end of the track, with the plunger against theend sto . When ready, release the plunger by tapping gently with a pencil or ruler. Start timingwith a stopwatch when the plunger is released, and stop timing when the predetermined distanceis covered Repeat the un 4-5 times (good data) and determine an average value for the time ofthe run.

3. Record the distance chosen. m

4. Record the mass of the cart. kg

5 Variation 1. CHANGING THE FORCEa) Collect data (see #2)with the spring plunger set to the first position. Record times.b) Collect data with the spring plunger set to the second position. Record times.c) Collect data with the spring plunger set to the maximum position. Record times.

6. Variation 2: CHANGING THE MASSCollect all these data values with the plunger set to the maximum position.a) Collect data for the cart with no mass added. (Data from previous step can be used)b) Record the mass of the cart with one mass bar added. Collect data (see #2). Record times.c) Record the mass of the cart with two bars added. Collect data. Record times.

Data Table.Mass= Mass= Mass= Mass- Mass=

SpringPosition:

Position 1 Position 2 Position 3 Position 3 Position 3

Time (s)-trialtTime (s)-tria!2Time (s)-trial3Time (s)-tnal4Time (s)-trials

[Type text]

Data Analysis and Questions:

For each variation ( ifferent spring positions and different masses), calculate the acceleration andthe force. (Big Hint The equation Ad = % at2 could be helpful)Show your calculations (with units); place resulting answers in the table.

Results table:

Mass at Pos.1 Mass at Pos 2 Mass at Pos.3 Mass at Pos.3 Mass at Pos 3

Avg. Time (s)

Acceleration.(m/ss)Force (N)

1. Usin your data for evidence/support, does the acceleration increase or decrease as the forceis increased? Is the change directly proportional?

2. Using your data for evidence/support, does the acceleration increase or decrease as the massis increased? Is the change directly proportional?

3. A scale shows that you weigh 525 N.a) What is your mass?

b) What would your mass be on the moon? (gmoon = 1.60 m/s )