Q: A 2 kg object is lifted from ground level to a height of 5 m. If $$g = 9.8\ \mathrm{m/s^2$}$$, what is the change in potential energy?

$$\Delta PE = 2 \times 9.8 \times 5 = 98\ \mathrm{J}$$

Q: A body of mass 3 kg is moving at a velocity of 4 m/s. What is its kinetic energy?

$$KE = \frac{1}{2} \times 3 \times 4^2$ = 24\ \mathrm{J}$$

Q: A rotating disk has a moment of inertia $$I = 0.5\ \mathrm{kg\cdot m^2$}$$ and angular velocity $$\omega = 10\ \mathrm{rad/s}. $$What is its kinetic energy?

$$KE = \frac{1}{2} \times 0.5 \times 10^2$ = 25\ \mathrm{J}$$

Q: A 1 kg block slides down a frictionless incline from a height of 10 m. What is its velocity at the bottom? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 10} = 14\ \mathrm{m/s}$$

Question 1

Which of the following statements best describes the law of conservation of mass in a closed system?

Accepted Answer

The mass entering the system is equal to the mass leaving the system, so the change in mass is zero.

Question 2

A 2 kg object is lifted from ground level to a height of 5 m. If $$g = 9.8\ \mathrm{m/s^2$}$$, what is the change in potential energy?

Accepted Answer

$$\Delta PE = 2 	imes 9.8 	imes 5 = 98\ \mathrm{J}$$

Question 3

Which equation correctly relates energy and mass according to Einstein's theory of relativity?

Accepted Answer

$$E = mc^2$

Question 4

A body of mass 3 kg is moving at a velocity of 4 m/s. What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2} 	imes 3 	imes 4^2$ = 24\ \mathrm{J}$$

Question 5

Which of the following is NOT a mode of heat transfer?

Accepted Answer

Compression

Question 6

In the context of thermodynamics, what is the definition of internal energy?

Accepted Answer

The total energy contained within a body, including molecular, atomic, and subatomic energies.

Question 7

A system absorbs 500 J of heat and does 200 J of work on its surroundings. What is the change in internal energy?

Accepted Answer

$$\Delta U = 500 - 200 = 300\ \mathrm{J}$$

Question 8

Which of the following best describes the difference between potential and kinetic energy?

Accepted Answer

Potential energy is stored energy due to position, while kinetic energy is energy due to motion.

Question 9

Which of the following is a correct statement about heat?

Accepted Answer

Heat is energy in transit due to a temperature difference.

Question 10

A rotating disk has a moment of inertia $$I = 0.5\ \mathrm{kg\cdot m^2$}$$ and angular velocity $$\omega = 10\ \mathrm{rad/s}. $$What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2} 	imes 0.5 	imes 10^2$ = 25\ \mathrm{J}$$

Question 11

Which of the following is true about energy conservation in thermodynamics?

Accepted Answer

Energy can neither be created nor destroyed, only transformed from one form to another.

Question 12

Which formula represents the change in internal energy for a process?

Accepted Answer

$$\Delta U = U_2$ - U_1$

Question 13

A 1 kg block slides down a frictionless incline from a height of 10 m. What is its velocity at the bottom? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 10} = 14\ \mathrm{m/s}$$

Question 14

Which of the following is a scalar quantity?

Accepted Answer

Energy

Question 15

Which process involves heat transfer between a solid surface and a moving liquid or gas?

Accepted Answer

Convection

Question 16

A system does 150 J of work and loses 50 J of heat to the surroundings. What is the change in internal energy?

Accepted Answer

$$\Delta U = -50 - 150 = -200\ \mathrm{J}$$

Question 17

Which of the following best describes the triple point in a phase diagram?

Accepted Answer

The temperature and pressure at which solid, liquid, and vapor phases coexist in equilibrium.

Question 18

Which of the following is the correct unit for energy in the SI system?

Accepted Answer

Joule

Question 19

Which statement about work in thermodynamics is correct?

Accepted Answer

Work is energy transferred by means other than heat.

Question 20

A gas expands in a piston, doing 400 J of work while absorbing 600 J of heat. What is the change in internal energy?

Accepted Answer

$$\Delta U = 600 - 400 = 200\ \mathrm{J}$$

Fundamentals of Thermodynamics 1: Energy and the First Law

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