Time Left:
600
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1. According to the law of conservation of energy, energy can be
A. Created and destroyed
B. Transformed from one form to another
C. Lost completely during conversion
D. Created by machines
2. The total energy before and after a transformation remains
A. Doubled
B. Decreased
C. Constant
D. Half
3. During free fall, potential energy of an object
A. Increases
B. Decreases
C. Remains constant
D. Becomes zero instantly
4. During free fall, the loss in potential energy appears as
A. Kinetic energy
B. Heat energy
C. Electrical energy
D. Magnetic energy
5. The total mechanical energy (potential + kinetic) of a freely falling body is
A. Zero
B. Constant
C. Increasing
D. Decreasing
6. At the highest point of a free fall, an object has
A. Only kinetic energy
B. Only potential energy
C. Both energies equal
D. No energy
7. When a freely falling object is just about to touch the ground, it has
A. Only potential energy
B. Only kinetic energy
C. Half kinetic and half potential energy
D. No energy
8. The total mechanical energy of a freely falling body ignoring air resistance is
A. Decreasing
B. Constant
C. Increasing
D. Zero
9. The expression for total mechanical energy of a body is
A. mgh + ½mv²
B. ½mv² + F×s
C. mgh – ½mv²
D. F×s – mgh
10. The term “rate of doing work” refers to
A. Force
B. Power
C. Energy
D. Velocity
11. The formula for power is
A. Work × Time
B. Force × Displacement
C. Work ÷ Time
D. Energy × Time
12. The SI unit of power is
A. Joule
B. Watt
C. Newton
D. Pascal
13. One watt is equal to
A. 1 joule per second
B. 1 newton per metre
C. 1 joule per hour
D. 1 newton per second
14. If a machine does 100 J of work in 2 seconds, its power is
A. 50 W
B. 100 W
C. 200 W
D. 25 W
15. Power of 1 kilowatt is equal to
A. 100 J/s
B. 1000 J/s
C. 10 J/s
D. 10,000 J/s
16. If two girls climb the same height but one does it faster, then
A. Both have equal power
B. Both have equal energy but different power
C. The slower one has more power
D. The faster one does less work
17. Power measures
A. The rate of energy transfer
B. Total energy used
C. The energy of motion
D. The total work done
18. A girl lifts a weight of 400 N to a height of 8 m in 20 s.Her power is
A. 160 W
B. 320 W
C. 80 W
D. 400 W
20. Average power is defined as
A. Total time ÷ total work
B. Total work ÷ total time
C. Work × Time
D. Force ÷ Distance
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