Work and energy are fundamental concepts in physics that describe how forces cause motion and how energy changes form. This chapter covers the definition of work, different forms of energy, the work-energy principle, power, efficiency, and energy resources. It also discusses renewable and non-renewable energy sources, their advantages, and their environmental impacts. The MCQs below help students review these essential concepts.
1. Work is said to be done when:
- A. A force is applied and displacement occurs ✅
- B. A force is applied without displacement
- C. Displacement occurs without force
- D. Energy remains constant
Explanation: Work is done when a force moves an object in the direction of the force.
2. The SI unit of work is:
- A. Joule ✅
- B. Newton
- C. Watt
- D. Meter
Explanation: One joule is the work done when a force of one newton moves an object one meter.
3. Power is defined as:
- A. Work done per unit time ✅
- B. Force × distance
- C. Energy stored
- D. Force per unit area
Explanation: Power measures how quickly work is done, in watts.
4. The SI unit of power is:
- A. Watt ✅
- B. Joule
- C. Newton
- D. Volt
Explanation: One watt is equal to one joule per second.
5. Which energy is due to motion?
- A. Kinetic energy ✅
- B. Potential energy
- C. Chemical energy
- D. Nuclear energy
Explanation: Kinetic energy is the energy of a moving object.
6. Potential energy depends on:
- A. Height and mass ✅
- B. Velocity only
- C. Temperature
- D. Pressure
Explanation: Potential energy = mgh, where m is mass, g is gravity, and h is height.
7. The work-energy principle states that:
- A. Work done equals change in kinetic energy ✅
- B. Work equals power × time
- C. Energy can be created
- D. Force equals work × time
Explanation: The net work done on an object changes its kinetic energy.
8. Renewable energy source is:
- A. Solar energy ✅
- B. Coal
- C. Natural gas
- D. Petroleum
Explanation: Solar energy is renewable and sustainable.
9. Non-renewable energy source is:
- A. Coal ✅
- B. Wind energy
- C. Solar energy
- D. Hydropower
Explanation: Coal is finite and cannot be replenished in a short time.
10. Efficiency is given by the formula:
- A. (Useful energy output ÷ Total energy input) × 100% ✅
- B. Work ÷ Power
- C. Force × distance
- D. Power × time
Explanation: Efficiency measures how much input energy is converted to useful work.
11. Hydroelectric power is generated by:
- A. Falling water ✅
- B. Burning fuel
- C. Nuclear reactions
- D. Wind turbines
Explanation: Hydroelectric dams convert the potential energy of water into electricity.
12. Which form of energy is stored in food and fuel?
- A. Chemical energy ✅
- B. Thermal energy
- C. Mechanical energy
- D. Sound energy
Explanation: Chemical energy is released during chemical reactions.
13. 1 kilowatt-hour is equal to:
- A. 3.6 × 10⁶ joules ✅
- B. 1000 joules
- C. 360 joules
- D. 3600 joules
Explanation: 1 kWh is the energy used by a 1 kW appliance in 1 hour.
14. Geothermal energy is obtained from:
- A. Heat inside the Earth ✅
- B. Sunlight
- C. Wind
- D. Oceans
Explanation: Geothermal plants use heat from Earth’s interior to produce electricity.
15. Which factor does NOT affect the amount of work done?
- A. Color of the object ✅
- B. Force applied
- C. Displacement
- D. Direction of force
Explanation: Work depends on force, displacement, and angle between them, not color.