Energy Transformations and Conservation Quiz

Grade 10 · Science · Quiz

Test your understanding of energy forms, transformations, conservation, and efficiency calculations.

Questions

1. A 5 kg object is held 10 m above the ground (g = 10 m/s²). What is its gravitational potential energy?

   1. 50 J
   2. 500 J
   3. 15 J
   4. 100 J
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   Answer: 500 J

   GPE = mgh = 5 kg × 10 m/s² × 10 m = 500 J.

2. All energy conversions in real-world systems are 100% efficient.

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   Answer: False

   All real-world energy conversions lose some energy as heat due to friction and resistance. 100% efficiency is a theoretical ideal never achieved in practice.

3. A toaster converts electrical energy primarily into:

   1. Chemical energy
   2. Kinetic energy
   3. Thermal energy
   4. Nuclear energy
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   Answer: Thermal energy

   A toaster converts electrical energy into thermal energy (heat) via resistance wires — the heat toasts the bread. Some radiant energy (light, infrared) is also emitted.

4. The rate at which work is done or energy is transferred is called ___.

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   Answer: power

   Power = Work / Time. Measured in Watts (W). It tells you how fast energy is being used or transferred.

5. A 3 kg object has 54 J of kinetic energy. What is its speed?

   1. 3 m/s
   2. 6 m/s
   3. 9 m/s
   4. 18 m/s
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   Answer: 6 m/s

   KE = ½mv² → 54 = ½ × 3 × v² → 54 = 1.5v² → v² = 36 → v = 6 m/s.

6. Chemical energy stored in food is transformed into kinetic and thermal energy in the human body.

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   Answer: True

   During digestion and metabolism, chemical energy from food is converted to kinetic energy for movement and thermal energy (body heat) — with some lost as waste heat.

7. The Law of Conservation of Energy states that energy cannot be created or ___.

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   Answer: destroyed

   The Law of Conservation of Energy: energy cannot be created or destroyed, only transformed. The total energy in a closed system is always constant.

8. A machine inputs 1,000 J and outputs 600 J of useful work. What is its efficiency?

   1. 40%
   2. 60%
   3. 167%
   4. 600%
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   Answer: 60%

   Efficiency = (useful output / total input) × 100% = (600 / 1000) × 100% = 60%. The remaining 40% (400 J) was wasted, typically as heat.

9. When a pendulum swings, it converts kinetic energy to potential energy and back, with total mechanical energy remaining constant (ignoring friction).

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   Answer: True

   In an ideal pendulum (no friction/air resistance), the pendulum continuously converts between maximum PE (at the top of its arc) and maximum KE (at the bottom), with total mechanical energy constant.

10. Which energy transformation occurs in a solar panel?

    1. Chemical to electrical
    2. Radiant to electrical
    3. Thermal to electrical
    4. Kinetic to electrical
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    Answer: Radiant to electrical

    Photovoltaic solar panels convert radiant energy (sunlight/photons) directly into electrical energy using the photovoltaic effect in semiconductor materials.

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