Work Energy And Power Question 197
Question: 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 [Kerala PET 2002]
Options:
A) 7.46 J
B) 7400 J
C) 7.46 ergs
D) 74.6 J
Show Answer
Answer:
Correct Answer: A
Solution:
Motor makes 600 revolution per minute
n = $ 600\frac{revolution}{minute}=10\frac{rev}{\sec } $ .
Time required for one revolution $ =\frac{1}{10} $ sec Energy required for one revolution = power × time = $ \frac{1}{4}\times 746\times \frac{1}{10}=\frac{746}{40}J $
But work done = 40% of input % $ =40\times \frac{746}{40}=\frac{40}{100}\times \frac{746}{40}=7.46J $
