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Practice Exam Answers

29 verified answers
21
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A 4400 cap w motor is used to do work. If the motor is used for 200 s , how much work could it do? (Power: cap p is equal to cap w over t )

A
22 cap j
B
4600 cap j
C
4200 cap j
D
880 comma 000 cap j
22
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Which occurs when a warm fluid cools down?

A
The mass of the fluid decreases.
B
Energy is absorbed from the environment.
C
Energy is released to the environment.
D
The density of the fluid decreases.
23

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 speeds up and then stops when air resistance equals gravity.
C
The object falls at a constant speed because only one force acts on it.
D
The object falls faster and faster until it strikes the ground.
24

Kai was 200 meters north of the library when he remembered he had to return some books to the library. It took him 200 seconds to do the round trip. Which best describes Kai’s roundtrip?

A
His speed was 2 m/s , and his velocity was 0 .
B
His speed was 1 m/s , and his velocity was 1 m/s north.
C
His speed was 1 m/s , and his velocity was 0.
D
His speed was 2 m/s ,, and his velocity was 2 m/s south.
25

Which statement best compares the speed of a sound wave moving through a pot of boiling water and the water vapor above the pot?

A
The sound wave would move faster through the water than through the water vapor.
B
The sound wave would move slower through the water than through the water vapor.
C
The sound wave would move through the water and water vapor at the same speed, but decrease in speed at the transition point.
D
The sound wave would move the same speed through the water and the water vapor.
26

What must be true in order for magnetism to induce an electric current in a wire?

A
The wire must be part of an open circuit.
B
The wire must be part of a closed circuit.
C
There cannot be a switch in the circuit.
D
There needs to be a switch in the circuit.
27

Which best contrasts an electric generator and an electric motor?

A
In a generator, slip rings function as a solenoid, and in a motor, an armature functions as a solenoid.
B
A generator converts electrical energy to kinetic energy, and a motor converts kinetic energy to electrical energy.
C
In a motor, slip rings function as a solenoid, and in a generator, an armature functions as a solenoid.
D
A generator converts kinetic energy to electrical energy, and a motor converts electrical energy to kinetic energy.
28

The total energy in a system is 675 J. The kinetic energy changes from 296 J to 432 J. Which statement best describes the potential energy of this system?

A
It changes from 296 J to 432 J.
B
It changes from 432 J to 296 J.
C
It changes from 243 J to 379 J.
D
It changes from 379 J to 243 J.
29

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

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