Q: A 3 kg brick is lifted from the floor to a shelf 1.5 m above the ground. What is the gravitational potential energy (PE) of the brick relative to the floor? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

$$PE = 3\ \mathrm{kg} \times 9.8\ \mathrm{m/s^2$} \times 1.5\ \mathrm{m} = 44.1\ \mathrm{J}$$

Q: A 0.2 kg baseball is dropped from a height of 5.0 m. What is its gravitational potential energy just before it is dropped? (Use $$g = 10\ \mathrm{m/s^2$})$$

$$PE = 0.2\ \mathrm{kg} \times 5.0\ \mathrm{m} \times 10\ \mathrm{m/s^2$} = 10\ \mathrm{J}$$

Q: A student lifts a 10 kg box to a shelf 2 m above the ground. How much work is done against gravity? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

$$W = 10\ \mathrm{kg} \times 9.8\ \mathrm{m/s^2$} \times 2\ \mathrm{m} = 196\ \mathrm{J}$$

Question 1

Which of the following best describes the Law of Conservation of Energy?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another.

Question 2

A 3 kg brick is lifted from the floor to a shelf 1.5 m above the ground. What is the gravitational potential energy (PE) of the brick relative to the floor? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$PE = 3\ \mathrm{kg} 	imes 9.8\ \mathrm{m/s^2$} 	imes 1.5\ \mathrm{m} = 44.1\ \mathrm{J}$$

Question 3

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

Accepted Answer

Kinetic

Question 4

A moving hammer strikes a nail and drives it into wood. Which type of energy transformation primarily occurs in this process?

Accepted Answer

Kinetic energy to work

Question 5

Which equation correctly relates mass and energy, as described by Einstein's famous formula?

Accepted Answer

$$E = mc^2$

Question 6

In a hydropower plant, what is the correct sequence of energy transformations from the reservoir to the power lines?

Accepted Answer

Gravitational potential energy $$\rightarrow$$ kinetic energy $$\rightarrow$$ mechanical energy $$\rightarrow$$ electrical energy

Question 7

Which of the following is the SI unit for energy?

Accepted Answer

Joule

Question 8

A 0.2 kg baseball is dropped from a height of 5.0 m. What is its gravitational potential energy just before it is dropped? (Use $$g = 10\ \mathrm{m/s^2$})$$

Accepted Answer

$$PE = 0.2\ \mathrm{kg} 	imes 5.0\ \mathrm{m} 	imes 10\ \mathrm{m/s^2$} = 10\ \mathrm{J}$$

Question 9

Which of the following devices converts chemical energy directly into electrical energy?

Accepted Answer

Battery

Question 10

Which process is an example of energy transfer by mechanical waves?

Accepted Answer

Sound traveling through air

Question 11

A student lifts a 10 kg box to a shelf 2 m above the ground. How much work is done against gravity? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$W = 10\ \mathrm{kg} 	imes 9.8\ \mathrm{m/s^2$} 	imes 2\ \mathrm{m} = 196\ \mathrm{J}$$

Question 12

Which of the following statements about power is correct?

Accepted Answer

Power is the rate at which energy is transferred.

Question 13

Which of the following is a real-life example of the transformation of kinetic energy into heat energy?

Accepted Answer

Friction between car brakes and wheels during braking

Question 14

Which of the following is an example of energy transfer by electromagnetic radiation?

Accepted Answer

Sunlight warming the Earth's surface

Question 15

Which of the following best describes the energy transformation in a solar cell?

Accepted Answer

Radiant energy to electrical energy

Question 16

A cup of hot coffee cools down when left on a table. Which mechanism is primarily responsible for the transfer of energy from the coffee to the surrounding air?

Accepted Answer

Heat conduction

Question 17

Which of the following is a correct statement about the First Law of Thermodynamics?

Accepted Answer

The total energy of an isolated system, including heat, is conserved.

Question 18

Which of the following is the correct formula for calculating work done by a constant force?

Accepted Answer

$$W = F \cdot d$$

Question 19

Which of the following is an example of the transformation of electrical energy into radiant energy?

Accepted Answer

A light bulb emitting light

Question 20

If a system's total energy decreases, what must have happened according to the law of conservation of energy?

Accepted Answer

Energy must have crossed the system's boundary by some mechanism.

Energy and Conservation Laws: Physics Study Notes

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