Bellringer

• Get out essentials and turn to homework

• Read article on your desk forces

• Write questions and answers in isn

Day 1Day 1

Motion, force, and massMotion, force, and mass

Force and Force and MotionMotion

Standard: 8-5The student will demonstrate

an understanding of the effects of forces on the

motion of an object. (Physical Science)

• 8-5.4 Predict how varying the amount of force or mass will affect the motion of an object

MotionMotion• What is motion?

– A change in the position of an object over time.

• How do you know something has moved?– You use a reference point!

• A stationary (not moving) object such as a tree, street sign, or a line on the road.

Did the beaver move?

•What causes an object to move?– A FORCE!– ALL motion is due to forces acting on

objects!

•What is a force?– A push or a pull

FORCE MOTION

Can more thanone force act onan object at the

same time?

#2

#3

#1

YES!Example: Gravity is

pulling you down to Earth, the ground is supporting you, and your legs moving you forward as you run during PE.

The total combination of the forces acting on an

object is called NET FORCE.

MassMass• Mass is how much matter is in something.

– You can physically touch matter.– The more matter there is, the more something will weigh.– It is not the same as weight -amount of gravity pulling on

an object.

• It’s harder to make a large object move or change the speed and direction of it when it’s moving.

QuestionsQuestions• What happens when I throw a

baseball and a bowling ball with the same force?

• Which one speeds up faster and why?

Lab: Motion After a Collision

p443 in text book• How is it possible for a 70-kg football

player to knock down a 110-kg player? The smaller player usually must be running faster. Mass makes a difference when two objects collide, but the speed of the objects also matters. Explore the behavior of colliding objects in this lab.

Lab Directions: Space yourself about 6 feet away from a partner. 1.Slowly roll a tennis ball on the floor toward your partner. Have your partner roll a tennis ball quickly into the tennis ball. What happens?2.Slowly roll a base ball on the floor toward your partner. Have your partner roll a base ball quickly into the tennis ball. What happens?3.Roll one tennis ball and the other student roll to hit the tennis ball with your ball what happened to both tennis balls4. Roll the base ball and hit it with the tennis ball and record what happens

Lab: Findings

• What happened when you rolled the fast moving tennis ball into the slow moving tennis ball?

• What happened when you rolled the fast moving baseball into the slow moving tennis ball?

• What happened when you rolled two tennis balls into each other at the same speed?

Day 2Day 2

Force, mass and motionForce, mass and motion

Force and Force and MotionMotion

Force Review

• If an object is in motion and more force is applied to it, the object will begin moving faster.

• If two objects have the same mass and a greater force is applied to one of the objects, the object which receives the greater force will change speeds more quickly. – Example – hit a ball harder it speeds up

Force Review

• If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for a gradual slowing down. – Example: bicycle brakes

Force Review

• Varying the amount of force applied to a moving object can also change the direction that the object is moving more or less quickly. – Example – baseball will change direction when

hit by a bat

Mass Review

• If a heavy (more massive) object is in motion, more force must be applied to get the object moving faster.

• If the same force is applied to two objects, the object with the smaller mass will change speeds more quickly. – For example if a baseball and a bowling ball

are thrown with the same force the baseball will speed up faster.

Mass Review

• In order to slow down or stop a heavier (more massive) object, the force on that object must be greater than for a less massive object. – Example – a small car will slow down more

quickly than a large truck

• It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass.

.

How much force gravity pulls on an object

The amount of matter in an object

Weight depends on location of object

Always constant (same) no matter the location.

Newtons (N)g, kg, mg

scale Balance

Yes on Earth - once you leave Earth your weight will change, but your mass will remain the same

Lab: marble Forces and Motion

page 471• Lean 2 meter sticks parallel, less than a marble

width apart on 3 stacked books. This is your ramp.

• Tap a marble so it rolls up the ramp. Measure how far up the ramp it travels before rolling back.

• Repeat step 2 using 2 books, 1 book, 0 books. The same person should tap with the same force each time.

• Make a table to record the motion of the marble for each ramp height.

Forces and Motion Lab Marble Roll Height

0

5

10

15

20

25

30

35

40

3 Books 2 Books 1 Book 0 Books

Marble

INCHES

Number of Books Stacked

Question

• What would happen if the ramp were perfectly smooth and level?

Exit Slip

• Explain how changes in mass effect the motion of an object.

Day 3Day 3

Force, mass and motion Force, mass and motion reviewreview

Balanced and Unbalanced Balanced and Unbalanced forcesforces

Force and Force and MotionMotion

Review

• True or False

If an object is in motion and more force is applied to it, the object will begin moving faster.

True or False

• If an object must be slowed down quickly, the force applied to the object must be greater than what is needed for gradual slowing down or stop

Mass

• If a heavy (more massive) object is in motion, more force must be applied to get the object moving______________.

(Faster/slower)

True or False

• It is more difficult to change the direction of a heavy moving object, than one that is lighter in mass.

Indicator:

• 8-5.5 Analyze the resulting effect of balanced and unbalanced forces on an object’s motion in terms of magnitude and direction.

Balanced ForcesBalanced Forces• A balanced force is one in which the

net force equals ZERO.• Do you think there will be any motion?

– NO!

• Examples:

25 Newtons 25 Newtons

Unbalanced Unbalanced ForcesForces• An unbalanced force is one in

which the net force is greater than zero.

• Do you think there will be any motion?– YES!

• Examples:

25 Newtons 40 Newtons 2 N

50N

Only an _______________ Only an _______________ force can change the force can change the motion of an object.motion of an object.

• Example: Your dog can cause you to move if he pulls with enough force.– His force is greater

than the force you’re using to stay in place

What would happen if an What would happen if an unbalanced force acted on unbalanced force acted on an object that’s already in an object that’s already in

motion?motion?• It will change the

speed or direction of the object.

• Example: Your little brother is riding his tricycle. You run up behind him and give him a push.– Your force adds to the

existing force causing him to speed up.

Unbalanced forces can Unbalanced forces can act in the act in the samesame

direction.direction.• Example: You’re pushing a cabinet across

the room with a force of 15 N. You’re friend is pulling with a force of 10 N.

• What is the NET FORCE?• What direction is the cabinet moving?

15 Newtons 10 Newtons

Unbalanced forces can Unbalanced forces can act in act in oppositeopposite

directions.directions.• Example: Two dogs are tugging on a

rope. One dog pulls with a force of 20N and the other pulls with a force of 25N.

• What is the NET FORCE?• What direction is the rope moving?

25 Newtons20 Newtons

When you have opposing

forces, the direction the

object moves is in the same

direction as the larger

force.