Question 1

Which of the following best describes the law of conservation of energy?

Accepted Answer

Energy cannot be created or destroyed; it can only be transformed from one form to another.

Question 2

A worker lifts a 20 kg box to a shelf 2 meters high. What is the gravitational potential energy gained by the box? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$392\ \mathrm{J}$$

Question 3

Which equation correctly expresses the work-energy theorem?

Accepted Answer

$$W = \Delta KE$$

Question 4

A car of mass $$1000\ \mathrm{kg} is $$moving at $$20\ \mathrm{m/s}. $$What is its kinetic energy?

Accepted Answer

$$400,000\ \mathrm{J}$$

Question 5

If the speed of an object is doubled, what happens to its kinetic energy?

Accepted Answer

It quadruples.

Question 6

Which of the following is NOT a form of mechanical energy?

Accepted Answer

Thermal energy

Question 7

A machine has an efficiency of 40%. If you input $$1000\ \mathrm{J} of $$energy, how much useful energy output do you get?

Accepted Answer

$$400\ \mathrm{J}$$

Question 8

Which of the following statements about machines is correct?

Accepted Answer

Machines can multiply force but not work.

Question 9

A 10-N ball is lifted vertically 3 meters, pushed up a 5-meter ramp, or carried up a set of stairs to the same height. In which case is the work done against gravity the greatest?

Accepted Answer

The work is the same in all three cases.

Question 10

Which of the following best explains why a lever can be used to lift a heavy object with a small force?

Accepted Answer

It allows a small force to be applied over a greater distance.

Question 11

A power plant wastes about 30% of its energy as heat. What is one way to improve its overall efficiency?

Accepted Answer

Use recycled energy to heat nearby buildings.

Question 12

Which of the following is the correct unit for power?

Accepted Answer

Watt

Question 13

A person runs up a flight of stairs in half the time as another person of the same mass. Compared to the slower person, the faster person:

Accepted Answer

Uses more power.

Question 14

Which of the following is a real-world example of the transformation of potential energy into kinetic energy?

Accepted Answer

A stretched bow releasing an arrow.

Question 15

A block is pulled with a force of $$50\ \mathrm{N}$$ over a distance of $$4\ \mathrm{m}. $$How much work is done?

Accepted Answer

$$200\ \mathrm{J}$$

Question 16

Which of the following statements about kinetic energy and momentum is true?

Accepted Answer

Momentum is a vector and can be canceled; kinetic energy is a scalar and cannot be canceled.

Question 17

A fuel cell produces electricity by:

Accepted Answer

Combining hydrogen and oxygen to produce electric current.

Question 18

Which of the following is an example of concentrated energy?

Accepted Answer

Nuclear power

Question 19

If a machine has an input force of $$10\ \mathrm{N}$$ applied over $$5\ \mathrm{m}$$ and an output force of $$25\ \mathrm{N}$$ over $$2\ \mathrm{m}$$, what is the work output?

Accepted Answer

$$100\ \mathrm{J}$$

Question 20

Which of the following best describes the main source of energy for most processes on Earth?

Accepted Answer

The Sun

Chapter 7: Energy – Conceptual Physics Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard