The time taken by an engine of power 10 kW to lift a mass of 200 kg to the height of 40 m is
Correct answer: C. 8 s
- A. 2 s
- B. 4 s
- C. 8 s
- D. 16 s
Explanation
Power (P) is defined as the rate of doing work. It is given by the formula P=W/t , where W is the work done and t is the time taken. Work done (W) is given by W=mgh, where m is the mass, g is the acceleration due to gravity, and ℎh is the height. Rearranging the formula for power, we get t=W/p . Substituting the given values, m=200kg, g=9.8m/s2, h=40m, and P=10kW=10,000W, we get t=10,000(200×9.8×40) =7.84s≈8s.Incorrect Options Explanation:(a) 2 s: This is too short a time for the given scenario.(b) 4 s: This value is also too short for the work described.(d) 16 s: This time duration is too long for the given scenario.
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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