Q. 164.7( 4 Votes )
A man carrying a bag of total mass 25kg climbs up to a height of 10m in 50 seconds. Calculate the power delivered by him on the bag.
displacement(s) = 10 m
time taken(t) = 50 s
As the man is working against gravity so force(F) applied is
mg= 25 kg × 10 m/s2 = 250 N
Power = work done/time taken
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Identify the wrong statement among the following. Rewrite them by making necessary corrections.
a) Work and energy have different units.
b) When an aero plane takes off, the work done by its weight is positive.
c) The potential energy of spring increases when it is extended and decreases when it is compressed.
d) If the work done by external forces on a system is negative then the energy of the system decreases.
e) When a body is falling freely from a height, its kinetic energy remains constant.
f) The unit of power is watt.AP - Physics & Chemistry