Question

A man of mass 80 kg climbs up a stair in 20 sec.On doing so the power generated by his leg muscles is 400 W. Find the number of steps he has climbed if each step has height of 10 cm(take g=10m/s2

Answer 1

Answer:

Potential energy=mass×acceleration due to gravity x−height

P.E.=m×g×h

According to the given condition -

m=80+20=100kg

g=9.8m/s

2

h=25×40=1000cm=1m

P.E=Work Done=100×9.8×1=980J

Power is rate of work done =

Time Taken

Work Done

=

20

980

=49J/s=49Watt