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Question
A man weighing 500 N carried a load of 100 N up a flight of stairs 4 m high in 5 seconds. What is the power?
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Solution
Weight of the man, (W1) = 500 N
Weight of the load, (W2) = 100 N
Height, (h) = 4 m
Time taken, (t) = 5s
So total weight,
W = W1 + W2
= (500 + 100) N
= 600 N
We can calculate the work done against gravity as,Work done by the man is = (total weight)(vertical distance)
= (600)(4)
= 2400 J
Now, we can calculate the power of the man as,
Power = `"Work done"/"Time"`
So ,
Power = `2400/5` W
= 480 W
So , the power of man is 480 W .
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