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CBSE Class 9 Answered

Calculate the work done.
Asked by Nishant | 19 Oct, 2013, 07:15: PM
Expert Answer
The boy first moves a distance of 1.5 km against the force of friction.
 
Hence, work done to cover this distance is
 
W1 = Fs = 5 × 1500 = 7500 J
 
Now, the boy moves along a circle of radius 100 m for one and a half cycle.
For one complete cycle, displacement is zero and hence the work done will be zero. Thus, the boy will do work for remaining half cycle only. That is,
 
W2 = 5 × 3.14 × 100 = 1570 J
 
Finally the boy moves forward for 2 km.
Hence, work done is
 
W3 = 5 × 2000 = 10000 J
 
Thus, the total work done by the boy is
 
W = W1 + W2 + W3 = 7500 + 1570 + 10000 = 19,070 J
Answered by Romal Bhansali | 21 Oct, 2013, 10:06: AM

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