arrow_backBack to Study Resources

Quiz Chapter 7: Energy and Power

10 questions · Form 3 Science Bab 7: Energy and Power

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. A rubber bowstring is pulled back with an average force of $100 N$ by a distance of $0.4 m$. How much elastic potential energy is stored in the bowstring?

  1. 20 J
  2. 40 J
  3. 80 J
  4. 250 J
Show answer

Answer: A

$E_e = 12 F x = 12 × 100 N × 0.4 m = 20 J$.

2. A student weighing $450 N$ climbs a staircase of vertical height $4 m$ in $6 seconds$. What is the useful power generated by the student?

  1. 1800 W
  2. 300 W
  3. 112.5 W
  4. 675 W
Show answer

Answer: B

Work $W = F × s = 450 N × 4 m = 1800 J$. Power $P = 18006 = 300 W$.

3. What happens to the potential energy of a roller coaster cart as it descends down a steep track slope?

  1. Potential energy increases and converts into elastic energy.
  2. Potential energy decreases and converts into kinetic energy.
  3. Potential energy remains constant while kinetic energy increases.
  4. Potential energy drops to zero immediately at the top of the slope.
Show answer

Answer: B

As height decreases, gravitational potential energy decreases while converting directly into kinetic energy (speeding up the coaster).

4. An electric motor takes 4 seconds to perform 800 J of work. What is the power output of the motor?

  1. 3200 W
  2. 800 W
  3. 400 W
  4. 200 W
Show answer

Answer: D

Power $P = Wt = 800 J4 s = 200 W$.

5. What is the rate at which work is done or energy is transferred called?

  1. Force
  2. Power
  3. Inertia
  4. Momentum
Show answer

Answer: B

Power is defined as the rate of doing work ($P = Wt$).

6. A worker pushes a crate with a constant horizontal force of $50 N$ across a smooth floor over a distance of $4 m$. How much work is done by the worker?

  1. 12.5 J
  2. 54 J
  3. 200 J
  4. 20 J
Show answer

Answer: C

Work $W = F × s = 50 N × 4 m = 200 J$.

7. What is the formula used to calculate the kinetic energy ($E_k$) of a moving object?

  1. $E_k = mgh$
  2. $E_k = 12 F x$
  3. $E_k = 12 m v2$
  4. $E_k = F × s$
Show answer

Answer: C

Kinetic energy of a mass $m$ moving at speed $v$ is given by $E_k = 12 m v2$.

8. A $1 kg$ rock is dropped from rest from a height of $20 m$. What is its kinetic energy right before it hits the ground? (Ignore air resistance, $g = 10 m s-2$)

  1. 20 J
  2. 100 J
  3. 200 J
  4. 400 J
Show answer

Answer: C

Gain in Kinetic Energy = Loss in Gravitational Potential Energy = $mgh = 1 × 10 × 20 = 200 J$.

9. In which of the following scenarios is NO work done according to physics definition?

  1. Lifting a $5 kg$ box from the floor onto a table
  2. Pushing a heavy concrete wall without moving it
  3. Pulling a toy car across the floor
  4. Climbing up a flight of stairs
Show answer

Answer: B

Work requires displacement in the direction of applied force ($W = F × s$). Since displacement is zero ($s = 0$), no work is done.

10. Using conservation of energy, calculate the velocity of a $0.5 kg$ ball dropped from a height of $5 m$ just before hitting the floor ($g = 10 m s-2$).

  1. $10 m s-1$
  2. $25 m s-1$
  3. $50 m s-1$
  4. $100 m s-1$
Show answer

Answer: A

$mgh = 12 m v2 arrow v = √2gh = √2 × 10 × 5 = √100 = 10 m s-1$.

Sponsored