AnswersPhysicsUnderstanding Energy

Practice Test Answers

8 verified answers
1
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Why is it important to know the direction of the force applied to a moving object and the direction in which the object is moving when determining the work done on the object?

A
When there is an angle between the two directions, the cosine of the angle must be considered.
B
A force at a right angle to the motion requires the use of the sine of the angle.
C
Only the component of the force perpendicular to the motion is used to calculate the work.
D
If the force acts in the same direction as the motion, then no work is done.
2
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What is the formula for calculating kinetic energy?

A
cap k cap e is equal to 1 half m v squared
B
cap k cap e is equal to 1 half m squared v
C
cap k cap e is equal to 2 m v squared
D
cap k cap e is equal to 2 m squared v
4

A spring that has a spring constant of 1400 cap n over m is stretched to a length of 2 point 5 m If the normal length of the spring is 1 point 0 m , how much elastic potential energy is stored in the spring?

A
1575 cap j
B
700 cap j
C
4375 cap j
D
1050 cap j
5

Earth and all of the air in the atmosphere around it make up an incredibly complex system. Energy is constantly changing forms in many different ways. How would scientists most likely describe the system of the Earth in regard to energy?

A
Earth is an isolated closed system because energy only escapes the system as heat travels into space.
B
Earth is an open system because heat energy from the Sun enters through the atmosphere.
C
Earth is an isolated closed system because the atmosphere allows energy from the Sun to enter as heat.
D
Earth is an open system because the atmosphere stops energy from escaping into space.
6

A bird flies off of a cliff, dropping a feather and knocking rocks off the cliff. The rocks reach the ground much faster than the feather. Which energy transformations occur in this case? Choose three correct answers.

A
Some of the potential energy of the feather is converted into kinetic energy.
B
All of the rocks’ potential energy is converted into kinetic energy because rocks do not experience wind resistance.
C
Some of the rocks’ potential energy is converted into thermal energy due to the friction of air resistance.
D
All of the feather’s potential energy is converted into thermal energy due to the friction of air resistance.
E
Some of the feather’s potential energy is converted into thermal energy due to the friction of air resistance.
7

Four different balls are moving at the same velocity. Which will have the greatest kinetic energy as it rolls?

A
a tennis ball
B
a bowling ball
C
a golf ball
D
a soccer ball
8

During which trial was the rock the highest above the ground?

A
1
B
2
C
3
D
4
10

How much thermal energy is generated?

A
2000 J
B
7000 J
C
1000 J
D
15,000 J

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