A) 7.46 J
B) 7400 J
C) 7.46 ergs
D) 74.6 J
Correct Answer: A
Solution :
Motor makes 600 revolution per minute \ n = \[600\frac{\text{revolution}}{\text{minute}}=10\frac{rev}{\sec }\] \ 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 \[=40%\times \frac{746}{40}=\frac{40}{100}\times \frac{746}{40}=7.46\,J\]
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