Unit Test — Unit test Answers

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4

best

i
increasing the inertia of the car
d
decreasing the reaction force
i
increasing the action force
d
decreasing the mass of the car
5

In a car, how does an air bag minimize the force acting on a person during a collision?

A
It increases the change in momentum of the person.
B
It decreases the change in momentum of the person.
C
It increases the time it takes for the person to stop.
D
It decreases the time it takes for the person to stop.
6

The information in the table represents the effect of the mass of two objects on the gravitational force between the two objects.Which number should be in the cell with the question mark?

Question illustration
A
The number is two because when you double the mass of one of the objects, the force between the objects is halved.
B
The number is four because when you double the mass of one of the objects, the force between the objects remains the same.
C
The number is eight because when you double the mass of one of the objects, the force between the objects also doubles.
D
The number is sixteen because when you double the mass of one of the objects, the force between the objects increases by a factor of 4.
7

Scientists launch a rocket, and they monitor its acceleration and the force exerted by its engines. As the rocket gets higher, the monitors show that the acceleration of the rocket is increasing but the force exerted stays the same. How do Newton’s laws explain why the scientists could expect this to happen?

A
The total force stays the same, but the action force is increasing as the reaction decreases.
B
The mass of the rocket decreases as fuel is burned, so the acceleration increases.
C
The inertia of the rocket increases, which reduces the force needed to change its speed.
D
The reaction force is increasing as fuel is burned, which causes a greater acceleration.
9

A tugboat is pulling a barge into a harbor. The barge is exerting a force of 3000 N against the tugboat.Which force would most likely allow the tugboat to move the barge into the harbor?

A
4500 N in the opposite direction of the barge
B
3000 N in the opposite direction of the barge
C
3000 N in the same direction of the barge
D
4500 N in the same direction of the barge
10

Which best describes a force?

A
a vector with magnitude and direction
B
a vector with speed and strength
C
a vector with direction only
D
a vector with strength only
11

Which describes an object’s speed when free falling in a vacuum?

A
The object accelerates until it reaches its terminal velocity.
B
The object falls at a constant speed because only one force acts on it.
C
The object falls faster and faster until it strikes the ground.
D
The object speeds up and then stops when air resistance equals gravity.
12

Levi and Clara are trying to move a very heavy box. Levi is pushing the box with a force of 30 N, and Clara is pulling the box with a force of 50 N. The box exerts a frictional force of 65 N.

A
There is a net force of 15 N against them and they cannot move the box.
B
There is a net force of 15 N allowing Levi and Clara to move the box.
C
There is a net force of 65 N against them and they cannot move the box.
D
There is a net force of 80 N allowing Levi and Clara to move the box.
14

A scientist on Earth drops a hammer and a feather at the same time an astronaut on the moon drops a hammer and a feather.

A
The hammer hits the ground before the feather on both Earth and the moon.
B
The hammer hits the ground before the feather on Earth, but the feather hits the ground first on the moon.
C
The hammer and the feather hit the ground together on both Earth and the moon.
D
The hammer hits the ground before the feather on Earth, and the hammer and feather hit at the same time on the moon.
15

Two objects collide and bounce apart. Assuming no outside forces act on the system, which best describes the total momentum after the collision?

A
It is always greater than it was before the collision.
B
It is often greater than it was before the collision.
C
It is always the same as it was before the collision.
D
It is often the same as it was before the collision.

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