The Vertical force is the same as his weight. By using the formula of work done and power, the correct answers are:
a.) 490N
b.) 147 KJ
c.) 122.5 W
Given that a boy of mass 50 kg runs up a hill of vertical height
300 m in 20 minutes.
a) The average vertical force he uses to lift himself up the hillside will be his normal reaction force (N) on the hill
N = mg
N = 50 x 9.8
N = 490N
b) the work he does climbing the hill will be
W = F x S
W = 490 x 300
W = 147000 Joules
W = 147 KJ
c) his average power will be
P = W/t
First convert the time from minutes to seconds
20 minutes = 20 x 60 = 1200 seconds
Substitute the time t and the work done W into the power formula
P = 147000/1200
P = 122.5 Watts
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