Bell RingerBell Ringer 2-1-102-1-10

1.1. Tell me the 4 types of friction. Tell me the 4 types of friction. (They were on the foldable!)(They were on the foldable!)

2.2. What is a force?What is a force?

3.3. Give an example of a force.Give an example of a force.

4.4. Is gravity a force? Why or why Is gravity a force? Why or why not?not?

Videos

Flight Attendant Fall Terminal Velocity Friction

Newton’s Newton’s Laws of Laws of MotionMotion

Ch. 10 Section 3Ch. 10 Section 3I.I. Law of Inertia Law of Inertia

II.II. F=MA F=MA

III.III. Action-Reaction Action-Reaction

While most people While most people know what Newton's laws know what Newton's laws say, many people do not say, many people do not know what they mean (or know what they mean (or simply do not believe what simply do not believe what they mean).they mean).

Newton’s Laws of MotionNewton’s Laws of Motion

11stst Law Law – An object at rest will stay – An object at rest will stay at rest, and an object in motion will at rest, and an object in motion will stay in motion at constant velocity, stay in motion at constant velocity, unless acted upon by an unbalanced unless acted upon by an unbalanced force.force.

22ndnd Law Law – – Force equals mass times Force equals mass times acceleration.acceleration.

33rdrd Law Law – – For every action there is For every action there is an equal and opposite reaction.an equal and opposite reaction.

11stst Law of Motion Law of Motion (Law of Inertia) (Law of Inertia)

An object at rest will An object at rest will stay at rest, and an object stay at rest, and an object in motion will stay in in motion will stay in motion at constant motion at constant velocity, unless acted upon velocity, unless acted upon by an unbalanced force.by an unbalanced force.

11stst Law Law InertiaInertia is the is the

tendency of an tendency of an object to resist object to resist changes in its changes in its velocity: velocity: whether in whether in motion or motion or motionless.motionless.

These pumpkins will not move unless acted on by an unbalanced force.

11stst Law Law

The moon will The moon will keep revolving keep revolving around the around the earth forever, earth forever, unless acted on unless acted on by an by an unbalanced unbalanced force.force.

• Moon in orbit around earth

11stst Law Law Once airborne, Once airborne,

unless acted unless acted on by an on by an unbalanced unbalanced force (gravity force (gravity and air – fluid and air – fluid friction) it friction) it would never would never stop!stop!

11stst Law Law

Unless acted Unless acted upon by an upon by an unbalanced unbalanced force, this golf force, this golf ball would sit ball would sit on the tee on the tee forever. forever.

Why then, do we Why then, do we observe every day objects observe every day objects in motion slowing down and in motion slowing down and becoming motionless becoming motionless without an outside force?without an outside force?

It’s a force we sometimes It’s a force we sometimes cannot see – friction.cannot see – friction.

Objects on earth, unlike Objects on earth, unlike the frictionless space the the frictionless space the moon travels through, are moon travels through, are under the influence of under the influence of friction.friction.

FrictionFriction

When the unbalanced When the unbalanced force is not obvious, force is not obvious, friction is probably the friction is probably the cause of the change in the cause of the change in the object’s motion. object’s motion.

There are four main types of friction:There are four main types of friction: Sliding friction: Sliding friction: ice skating Rolling friction: Rolling friction: bowling Fluid friction (air or liquid): Fluid friction (air or liquid): air or water resistance Static friction: Static friction: initial friction when moving an

object

What is this unbalanced force that acts on an What is this unbalanced force that acts on an object in motion?object in motion?

ExampleExample

Slide a book across a Slide a book across a table and watch it table and watch it slide to a rest slide to a rest position. The book position. The book comes to a rest comes to a rest because of the because of the presencepresence of a force - of a force - that force being the that force being the force of friction - force of friction - which brings the book which brings the book to a rest position. to a rest position.

In the absence of a force of In the absence of a force of friction, the book would continue friction, the book would continue in motion with the same speed in motion with the same speed and direction - forever! (Or at and direction - forever! (Or at least to the end of the table top.) least to the end of the table top.)

Newtons’s 1Newtons’s 1stst Law and Law and YouYou

(Don’t let this be you. Wear seat (Don’t let this be you. Wear seat belts.)belts.)

Because of inertia, objects (including Because of inertia, objects (including you) resist changes in their motion. you) resist changes in their motion. When the car going 80 km/hour is When the car going 80 km/hour is stopped by the brick wall, your body stopped by the brick wall, your body keeps moving at 80 km/hour.keeps moving at 80 km/hour.

22ndnd Law LawForce equals mass times acceleration.

22ndnd Law Law

The net force of an The net force of an object is equal to the object is equal to the product of its mass and product of its mass and acceleration, or F= m x a.acceleration, or F= m x a.

22ndnd Law Law

When mass is in kilograms and When mass is in kilograms and acceleration is in m/sacceleration is in m/s22, the unit of , the unit of force is in newtons (N).force is in newtons (N).

One newton is equal to the force One newton is equal to the force required to accelerate one kilogram required to accelerate one kilogram of mass at one m/sof mass at one m/s22..

22ndnd Law (F = M x A) Law (F = M x A)

How much force is needed to accelerate a 1400 Kilogram car 2 m/s2?

1. Write the formula1. Write the formula F = M x A2. Fill in given numbers and units2. Fill in given numbers and units F = 1400Kg x 2 m/s2

3. Solve for the unknown3. Solve for the unknown 2800 Kg- m/s2 or 2800 N

Bell Ringer Work on Chapter 10 Vocabulary

quickly. If you do not finish, you will

need to finish for homework. If you have already finished, sit

quietly and make sure your notebook is complete!

If mass remains constant, doubling the acceleration, doubles the force. If force remains constant, doubling the mass, halves the acceleration.

Newton’s 2nd Law proves that different masses accelerate to the earth at the same rate, but with different forces.

• We know that objects with different masses accelerate to the ground at the same rate.

• However, because of the 2nd Law we know that they don’t hit the ground with the same force.F = maF = ma

98 N = 10 kg x 9.8 98 N = 10 kg x 9.8 m/s2m/s2

F = maF = ma

9.8 N = 1 kg x 9.8 m/s9.8 N = 1 kg x 9.8 m/s22

Check Your Check Your UnderstandingUnderstanding

1.1. What is the force on a 1000 kg elevator that is What is the force on a 1000 kg elevator that is falling freely at 9.8 m/sfalling freely at 9.8 m/s22.?.?

2.2. What acceleration will result when a 12 N net What acceleration will result when a 12 N net force is applied to a 3 kg object? force is applied to a 3 kg object?

3.3. A net force of 16 N causes a mass to accelerate A net force of 16 N causes a mass to accelerate at a rate of 5 m/sat a rate of 5 m/s22. Determine the mass.. Determine the mass.

4.4. How much force is needed to accelerate a 66 kg How much force is needed to accelerate a 66 kg skier 1 m/sskier 1 m/s22??

  

Check Your Check Your UnderstandingUnderstanding

11. . What acceleration will result when a 12-N net force What acceleration will result when a 12-N net force applied to a 3-kg object? applied to a 3-kg object?

12 N = 3 kg X 4 m/s12 N = 3 kg X 4 m/s22    2. A net force of 16 N causes a mass to accelerate at a 2. A net force of 16 N causes a mass to accelerate at a

rate of 5 m/s2. Determine the mass.rate of 5 m/s2. Determine the mass. 16 N = 3.2 kg x 5 m/s16 N = 3.2 kg x 5 m/s22

   3. How much force is needed to accelerate a 66-kg skier 3. How much force is needed to accelerate a 66-kg skier

1 m/sec/sec?1 m/sec/sec?66 kg-m/s66 kg-m/s22 or 66 Nor 66 N

4. What is the force on a 1000-kg elevator that is falling 4. What is the force on a 1000-kg elevator that is falling freely at 9.8 m/sec/sec.?freely at 9.8 m/sec/sec.?

 9800 kg-m/s9800 kg-m/s22 or 9800 Nor 9800 N

Vocabulary p. 366 Vocabulary p. 366 Sections 1-4 (20 words)Sections 1-4 (20 words)

Chapter 10 Section 4 Notes

Newton’s 3Newton’s 3rdrd Law of Law of Motion/ Action-Motion/ Action-Reaction LawReaction Law

For every action, there is For every action, there is an equal and opposite an equal and opposite reaction.reaction.

33rdrd Law LawAccording to According to

Newton, whenever Newton, whenever objects A and B objects A and B interact with each interact with each other, they exert other, they exert forces upon each forces upon each other. When you sit other. When you sit in your chair, your in your chair, your body exerts a body exerts a downward force on downward force on the chair and the the chair and the chair exerts an chair exerts an upward force on upward force on your body. your body.

33rdrd Law Law

There are two There are two forces resulting forces resulting from this from this interaction - a interaction - a force on the force on the chair and a force chair and a force on your body. on your body. These two forces These two forces are called are called actionaction and and reactionreaction forces.forces.

Newton’s 3rd Law in Newton’s 3rd Law in NatureNature

Think about a fish swimming Think about a fish swimming in water.in water.

A fish uses its fins to push A fish uses its fins to push water backwards. In turn, the water backwards. In turn, the water water reactsreacts by pushing the by pushing the fish forwards, propelling the fish forwards, propelling the fish through the water.fish through the water.

The size of the force on the The size of the force on the water equals the size of the water equals the size of the force on the fish.force on the fish.

The direction of the force on The direction of the force on the water (backwards) is the water (backwards) is opposite the direction of the opposite the direction of the force on the fish (forwards).force on the fish (forwards).

33rdrd Law Law

Flying gracefully Flying gracefully through the air, through the air, birds depend on birds depend on Newton’s third Newton’s third law of motion. As law of motion. As the birds push the birds push down on the air down on the air with their wings, with their wings, the air pushes the air pushes their wings up their wings up and gives them and gives them lift.lift.

Consider the flying motion of birds. A bird Consider the flying motion of birds. A bird flies by use of its wings. The wings of a flies by use of its wings. The wings of a bird push air downwards. In turn, the air bird push air downwards. In turn, the air reacts by pushing the bird upwards. reacts by pushing the bird upwards.

The size of the force on the air equals the The size of the force on the air equals the size of the force on the bird; the direction size of the force on the bird; the direction of the force on the air (downwards) is of the force on the air (downwards) is opposite the direction of the force on the opposite the direction of the force on the bird (upwards).bird (upwards).

Action-reaction force pairs make it Action-reaction force pairs make it possible for birds to fly.possible for birds to fly.

Other examples of Other examples of Newton’s Third LawNewton’s Third Law

The baseball The baseball forces the bat forces the bat to the left (an to the left (an action).action).

The bat forces The bat forces the ball to the the ball to the right (the right (the reaction). reaction).

33rdrd Law Law Consider the Consider the

motion of a car on motion of a car on the way to school. the way to school. A car is equipped A car is equipped with wheels which with wheels which spin forward. As spin forward. As the wheels spin, the wheels spin, they grip the road they grip the road and push the road and push the road backwards.backwards.

33rdrd Law LawThe reaction of a The reaction of a rocket is an rocket is an application of the application of the third law of motion. third law of motion. Various fuels are Various fuels are burned in the burned in the engine, producing engine, producing hot gases. hot gases.

The hot gases push The hot gases push against the inside against the inside tube of the rocket tube of the rocket and escape out the and escape out the bottom of the tube. bottom of the tube. As the gases move As the gases move downward, the downward, the rocket moves in the rocket moves in the opposite direction.opposite direction.

Momentum Momentum = mass x veloctiy The SI unit for momentum is kg x m/s

and the direction.

Ex. 58 kg bike traveling east at 12 m/s. What is the momentum?

Answer: 696 kg x m/s east

Momentum increases if the mass or velocity of the object increases.

                                                                                                                 

1. Who was the scientist who gave us the Laws of Motion?

2. How many Laws of Motion are there?

3. What is another name for the third law of motion?

4. Which law explains why we need to wear seatbelts?

5. Which law says that force is equal to mass times acceleration (F = M x A)?

6. Which law says that heavier objects require more force than lighter objects to move or accelerate them?

7. Which law explains how rockets are launched into space?

8. Which law says that for every action there is an equal and opposite reaction?

1. Sir Isaac Newton 2. three 3. Action-Reaction Law4. First Law of Motion 5. Second Law of Motion 6. Second Law of Motion 7. Third Law of Motion 8. Third Law of Motion

Exit Quiz # 4Fill in the blanks for questions 1 and 3.1. Newton’s 1st Law: An object at rest must

stay at rest, and an object in motion must stay in motion, at constant velocity, unless acted on by an unbalanced ______.

2. If a 0.5 kg leaf falls from a tree at an acceleration of 1 m/s2, what is the force with which it hits the ground? (Remember F = m x a.)

3. Newton’s 3rd Law: For every action there is an equal and _______ reaction.

4. What unit measures force?