Forces and motion

​Horizontal forces act on two boxes, initially at rest, as shown. The magnitude and direction of the horizontal forces are also shown.
​What happens to Box X and Box Y as a result of the forces?​

• Box X starts moving, speeding up, and Box Y remains at rest.

• Box X starts moving at constant speed, and Box Y remains at rest.

• Box X starts moving at constant speed, and Box Y starts moving, speeding up.

• Box X starts moving, speeding up, and Box Y starts moving at a constant speed.

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An object moves at a constant speed.
​What will happen to this object's motion over time if no new forces are applied?

• It will change direction.

• It will increase in speed.

• It will decrease in speed.

• It will maintain a constant speed.

Look at the picture of a person about to kick a soccer ball. Then drag and drop the pins to correctly complete Newton’s Second Law as it is being applied to the soccer ball.​ ​ ​ ​

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​ (a)   ​ ​ ​ ​ (b)   Mass ​ ​ (c)   ​ ​ ​ ​ (d)   ​

• Force
• Acceleration
• =
• X
• /

Drag and drop the pins into the correct pictures to explain how Newton’s First Law works.

1st picture​ (a)   ​ ​2nd picture (b)   ​ 3rd picture (c)  

• An object at rest
• Applying a force to an object
• Force stopping a moving object

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NGSS.MS-PS2-2

Drag and drop the pins to correctly identify the principles of Newton’s Third Law.​ ​ ​1.

2.

a

d

Reaction: Balloon is forced upward

Action: Air rushes upward

Reaction balloon is forced downward

Action: air rushes downward

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NGSS.MS-PS2-1

Identify the action and reaction forces for the rocket.

a

b

REACTION FORCE

ACTION FORCE

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A leaf fell from a tree branch. The path it followed is shown in the diagram below.

• Objects with irregular shapes never fall in straight lines.

• Air currents and gravity applied changing and unbalanced forces to the leaf.

• The upward force of the air on the leaf was greater than the downward force of gravity.

• Once the leaf was in motion, it continued moving in the same direction because the forces were balanced.

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A disgruntled biology student drops his textbook out of a second story window. Why does it fall to the ground?

• The net force acting on the book by gravity is downward.

• The drag force of the air pulls it down.

• Because the student let go of the book.

• There is a strong magnetic force between the book and the ground.

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NGSS.MS-PS2-2

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NASA’s space shuttle program was active from 1981 until 2011. The photograph shows rockets carrying a space shuttle off the launchpad.

• As the fuel burns, gases push against the rocket, moving it upward.

• As the fuel burns, gases move out of the rocket and reduce air resistance.

• As the fuel burns, the mass of the rocket decreases.

• As the fuel burns, the rocket moves faster.

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NGSS.MS-PS2-1

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A heavyweight boxer winds up and punches a punching bag. Which of the following are true?

• The fist exerts more force than the punching bag.

• The force acting on the bag is equal and opposite to the force acting on the fist.

• The fist creates the action force and the punching bag creates the reaction force.

• There is no force between the two objects because they are balanced.

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