Unit 8.1 Quiz 4

A baseball player swings their bat and makes contact with a baseball. Which experiences a greater peak force?

• Neither. They exert an equal amount of force on each other.

• The bat applies a greater force on the ball.

• The ball applies a greater force on the bat.

• There is no way to know without measuring with a force meter.

Answer explanation

According to Newton's third law, for every action, there is an equal and opposite reaction. Therefore, the bat and the ball exert equal forces on each other at the moment of contact.

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NGSS.MS-PS2-2

When any two objects make contact, each object applies a force on the other surface they touch. The size and direction of those forces are:

• different size and in the same direction.

• different size and in opposite directions.

• the same size and in the same direction.

• the same size and in opposite directions.

Answer explanation

According to Newton's Third Law, when two objects interact, they exert forces that are equal in size but opposite in direction. Therefore, the correct answer is 'the same size and in opposite directions.'

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NGSS.MS-PS2-1

In a collision, if the mass of one of the objects is decreased: 

• the contact forces between the objects decrease.

• the contact forces between the objects increases.

• the contact forces between the objects do not change.

• the contact forces on only one of the objects decreases.

Answer explanation

In a collision, if the mass of one object decreases, its inertia reduces, leading to a decrease in the contact forces between the objects. Thus, the correct answer is that the contact forces between the objects decrease.

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NGSS.MS-PS2-1

NGSS.MS-PS2-2

In a collision, if the speed of one of the objects is increased:

• the contact forces between the objects do not change.

• the contact forces between the objects decrease.

• the contact forces between the objects increase.

• the contact forces on only one of the objects increases.

Answer explanation

In a collision, increasing the speed of one object results in greater momentum transfer, leading to increased contact forces between the objects. Thus, the correct choice is that the contact forces between the objects increase.

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NGSS.MS-PS2-2

Force is needed:

• for a motionless object to remain still.

• for a moving object to change its speed.

• for a moving object to keep moving at the same speed and direction.

• to prevent a moving object from turning.

Answer explanation

Force is required to change the speed of a moving object, as per Newton's second law. An object in motion will continue at the same speed and direction unless acted upon by an external force.

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NGSS.MS-PS2-2

If a 60 kg roller skater pushes a 30 kg roller skater with a force of 5 N rightward as shown in the diagram, then what will be the magnitude and direction of the force exerted by the 30 kg roller skater on the 60 kg roller skater be?

• 0 N

• 5 N leftward

• 5 N rightward

• 10 N

Answer explanation

According to Newton's third law, the force exerted by the 30 kg skater on the 60 kg skater is equal in magnitude and opposite in direction to the force applied. Thus, it is 5 N leftward.

Tags

NGSS.MS-PS2-1

When a soccer player heads the ball, how would the forces on the soccer player’s head compare to the forces on the ball?

• The forces on the head would be greater.

• The forces on the ball would be greater.

• The forces would be equal.

• There would only be forces on the ball.

Answer explanation

According to Newton's third law, for every action, there is an equal and opposite reaction. When a player heads the ball, the force exerted on the ball is equal to the force exerted on the player's head, making the forces equal.

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A previous question asked "During a header, how would the forces on the soccer player’s head compare to the forces on the ball?" Explain your answer to that question:

• The forces would cancel each other out.

• The head is more rigid (or harder) than the ball.

• The ball is the only thing moving.

• Forces come in equal and opposite pairs.

Answer explanation

According to Newton's third law, forces come in equal and opposite pairs. When a soccer player heads the ball, the force exerted by the player's head on the ball is matched by an equal force exerted by the ball on the player's head.

Tags

NGSS.MS-PS2-1