Common Core Standard
Middle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

HOW DO FORCES AFFECT MOTION?
A force is a push or pull on an object. Forces usually cannot be seen but their effects can.
Nothing moves, changes speed, stops or changes direction without force. Heavier objects need moreforce to get them to move or change direction.
Look at the examples below. Fill in the blanks with the correct force at work (push / pull).

What forces are at work?
The operator uses agrabber bucket to pick up thelarge rock.
The operator _________ thebucket and thumb against therock to get a tight grip.

bucketthbum

He then is able to ________ therock off the ground.

gr
ap

pleclawtineWhat forces are at work?
The operator _________the tinesof the grapple claw together to grip
the boulder.
The tines _________ against theboulder forming a tight grip. This
allows the operator to pick up theboulder.

.

elhildrWhat forces are at work?
The rotary drill is well equippedto drill in hard or soft rockapplications.
The drill head _________
through the material.

adCommon Core StandardMiddle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Newton’s 1st Law of Motion(the law of inertia)
Newton’s First Law of Motion states that an object at rest will remain at rest unless acted upon by
an unbalanced force. An object in motion continues in motion in the same direction and with thesame speed unless acted upon by an unbalanced force.
Friction is a force that slows down the motion of a moving object. Think about a land slide.
Once a slide begins the rock, earth and debris will stay in motion until friction between the material
and the ground slows the movement. Eventually, friction and gravity will work together to stop themotion of the slide.
Gravity is a force that pulls two objects toward each other because of their mass.
Mass is the measurement of the amount of material (matter) that makes up an object.

Friction and gravity are at work in each picture. Explain how each are at work and how they work
together.
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Common Core Standard
Middle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Multiple forces can act upon an object at the same time, pushing and pulling in any direction.
The strength and direction of the forces determine what happens to the object.
When more than one force acts upon an object, the forces combine to form a net force.
Forces may work together or they may be opposite forces.
Net force of zeroIf two forces of equal strength act upon an object in opposite directions, the forces will cancel eachother, resulting in a net force of zero and no movement.
Same force from the rightTheobject

Same force from the left

Net force is zero

Balanced forces - Two or more opposite forces are balanced forces if their effects cancel eachother and do not cause a change in an object's motion.
If these two identical compact track loaders play a game of tug of war moving forward at the same
speed, which machine would win the game? Why? Explain your answer.

Compact trackloaders

ANSWER___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________3Common Core Standard
Middle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Unbalanced forces - If one force is stronger and the effects of the forces don't cancel each other,
the forces are unbalanced. Unbalanced forces cause a change in motion, speed and/or direction.
A larger force causes a larger change in motion.
If the mini hydraulic excavator and the large excavator play a game of tug of war, which machine do
you think would win? Why? Explain your answer.

Mini hydraulic excavator
Weight = 3241 lbs.

Excavator
Weight = 190,016 lbs.

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Common Core Standard
Middle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Forces can make an object change shape.

hmamer

The hammer is used to breakup material like
concrete and rock.
What force is at work in thispicture? (push / pull)________How do the rocks change
shape as they break?
Name two more objects thatchange shape when a push orpull force is applied.

ANSWER_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

The wind is blowing the Catflag as it flies high above theship.
What force is at work in thispicture? (push / pull)___________How could the force cause theflag to change shape?

YOUR ANSWER_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

5Common Core StandardMiddle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Newton’s Second Law of Motion
Newton’s Second Law of Motion states that acceleration is produced when a force acts on amass. The greater the mass the greater the amount of force needed to accelerate the object.
More force is required to move a heavier object than a lighter object.
Newton’s Second Law of Motion gives us an exact relationship between force, mass andacceleration. It can be expressed as a mathematical equation.
F = M x A or Force = MASS X ACCELERATIONShow your work here.

Bob uses a telehandler to pull his 1,000lb. trailer to his barn. Bob travels at 10 mph. How much force
is exerted on the telehandler?

Show your work here.

During a race, the driver of the No. 31 Caterpillar Chevrolet runs an average speed of 170 mph in aSprint car that weighs about 3,300 lbs. How much force is exerted on the car?

6Common Core Standard
Middle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Weight is a measurement of how hard the earth’s gravity pulls on an object’s mass. The more mass
an object has, the more it weighs.
more mass = more pull = more weight
Which load shown below has a heavier mass? Why? Explain your answer.

Block handler

Wheel loader

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7Common Core StandardMiddle School - PS2.A:Forces and Motion
CC.6.W.1 Text Type & Purposes
CC.7.W.1 Text Type & Purposes
CC.8.W.1 Text Type & Purposes

Newton’s Third Law of Motion
Newton’s Third Law of Motion states for every action there is an equal and opposite reaction.
For every force, there is a reaction equal in size that moves in the opposite direction. When anobject pushes another object, it gets pushed back equally hard but in the opposite direction.

The propellers on this U.S. Navy patrol boat
push against the water with the force of its
powerful Cat marine engines.
What is the reaction? In what direction does theforce push the boat? Explain your answer.

As the Cat vocational truck drives to a worksite
its tires push against the road.
What is the reaction? In what direction does
the force push the truck? Explain your answer.

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