Force and Motion Review

Match the following

• unbalanced forces

• When all of the forces on an object cancel each other out

• weight

• Forces that do not cancel each other out when acting together on a single object

• balanced forces

• A measure of how much gravity exists between the earth and an object

• momentum

• The strength or force that something has when it is moving, due to its mass and velocity.

• gravity

• This force always pulls objects towards the center of the earth.

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Match the following

• Newton's Third Law

• states that the acceleration of an object is related to the mass of the object and the force applied to it.

• Newton's First Law

• states that an object at rest will stay at rest, and an object in motion will stay in motion, unless an outside force acts on it.

• Newton's Second Law

• states that for every action, there is an equal and opposite reaction.

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NGSS.MS-PS2-1

An object with a higher mass will require ​ (a)   force.

An object with a lower mass will require ​ (b)   force.

• more

• less

Answer explanation

An object with a higher mass requires more force due to its greater inertia, while an object with a lower mass requires less force to achieve the same acceleration, according to Newton's second law of motion.

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NGSS.MS-PS2-2

Tommy is comparing force and mass. He wrote down the mass of each object below.

If the same force is applied, on the same surface, put the masses below in order from which object will roll the farthest (1) to the shortest (5)

• 420 grams

• 600 grams

• 58 grams

• 46 grams

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NGSS.MS-PS2-2

If you apply force in the same direction that an object is moving, it will ​ (a)  

If you apply force in the opposite direction that an object is moving, it will ​ (b)  

• speed up

• slow down or stop

• stay the same speed

Answer explanation

Applying force in the same direction as an object's motion increases its speed, hence it will speed up. Conversely, applying force in the opposite direction slows it down or can stop it.

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NGSS.MS-PS2-2

The equation that correctly expresses Newton's 2nd law is:

• force=mass-acceleration

• force=mass/acceleration

• force=mass + acceleration

• force=mass x acceleration

Answer explanation

Newton's 2nd law states that force equals mass times acceleration (force = mass x acceleration). This means that the force acting on an object is directly proportional to its mass and the acceleration it experiences.

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NGSS.HS-PS2-1

Janet is rolling a bowling ball and a tennis ball down the hallway.

Why would she need to apply more force to the bowling ball than she did to the tennis ball?

• The difference in the friction

• The difference in the mass

• The different in the gravity

• She would not need to apply more force.

Answer explanation

Janet needs to apply more force to the bowling ball than the tennis ball because the bowling ball has a greater mass. According to Newton's second law, more mass requires more force to achieve the same acceleration.

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NGSS.MS-PS2-2

Will it take more force to push an empty shopping cart or a shopping cart that is full?

• The empty shopping cart

• The full shopping cart

• They will take the same amount of force

Answer explanation

It will take more force to push a full shopping cart because it has greater mass. According to Newton's second law, more mass requires more force to accelerate, making the full cart harder to push than the empty one.

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NGSS.MS-PS2-1

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Which shopping cart will have more acceleration?  

• The empty shopping cart

• The shopping cart that's full

• They will be the same

Answer explanation

The empty shopping cart has less mass than the full one. According to Newton's second law, acceleration is inversely proportional to mass when the same force is applied. Therefore, the empty cart will accelerate more.

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NGSS.MS-PS2-1

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Why would one ball travel a greater distance than the other when pushed with the same amount of force?

• Different sizes

• Different weights

• Different masses

• Different forces

Answer explanation

The ball with different mass will experience different acceleration when the same force is applied, according to Newton's second law (F=ma). A lighter ball accelerates more, allowing it to travel a greater distance.

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NGSS.MS-PS2-1

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