A quarter horse power motor runs at a speed of 600 r . p . m . Assuming 40% efficiency the work done by the motor in one rotation will be

Options

A. 7.46 J
B. 7400 J
C. 7.46 ergs
D. 74.6 J

Answer

A

Explanation

Motor makes 600 revolution per minute
`therefore n= 600 = ("revolution")/("minute")= 10 ("rev")/(sec)`
`therefore` Time required for one revolution `=(1)/(10)` sec
Energy required for one revolution = power `xx` time
`=(1)/(4) xx 746 xx (1)/(10)= (746)/(40)J`
But work done= 40% of input
`=40% xx (746)/(40)= (40)/(100) xx (746)/(40)= 7.46J`