An electric motor is required to haul a cage of mass 400kg up a mineshaft through a vertical height of 1200m in 2 minutes. What will be the electrical power required if the overall efficiency is 80%?
Correct answer: C. 32kw
- A. 3.2kw
- B. 5kw
- C. 32kw
- D. 50kw
Explanation
The electrical power can be found using the formula:Pelectrical= W/ ΔtWhere W is the work doneΔt is the time taken.We may write:W= mghSoPelectrical=mgh/ ΔtNow,Actual power= Pelectrical/ efficiency
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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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