Question

Swaralee takes 20 seconds to carry a bag weighing 20 kg to a height of 10 metre. Find the power she has used?

Answer 1

Power = Work done by her / Time
= mgh / t
= (20 * 9.8 * 10) / 20
= 98 Watt

[Note: If g = 10m/s^2 then Power = 100 Watt]

Answer 2

here see we all know that work kinetic energy and potential energy is inter convertible and so when work is done there work convert into potential energy and kinetic energy so in this question work is done by person bag is not work itself so here it's kinetic energy is zero and it's work done is change into potential energy so we can write here,
work = potential energy change
= mg(h2-h1)
= ,20×10× (10-0)
because we take here h1 as frame of reference so h1= 0
work= 2000J

and we know that power is work/time
power = 2000/20
= 100 J/S