Mohan lifts his cellphone to a height of 1 m

cbse
workandenergy

#1

Mohan lifts his cellphone to a height of 1 m. He takes 1 s to do this. After lowering the phone, he then lifts it 2 m in 2 s. Has he generated more power in doing the second task? Give reason to justify your answer.


#2

Let, mass of cellphone be m kg
Work done (W) by Mohan = mgh
where, h = height at which cellphone is raised and
g = acceleration due to gravity
=> W = mg X 1 = mg
Power delivered =Work done / time = mg / 1 = mg
Work done to lift cellphone by 2 m = mg X 2 = 2mg
Power delivered =Work done / time = 2mg / 2 = mg
So, in both cases power delivered by Mohan is same.