Question

What is the average power output of a weight lifter who can lift 260 kg from the floor to a height of 1.60 m in 1.7 seconds?

Answer 1

The power P is the amount of work W done in a certain amount of time t

`P= (W)/(t)`
For the law of conservation of energy, the amount of work done by the lifter is equal to the difference in gravitational potential energy of the block of mass
`m=260 kg` between its final location (height h=1.60 m) and its initial location (the floor, h=0). This potential energy difference is

`\Delta U = mgh_f-mgh_0 =(260 kg)(9.81 m/s^2)(1.60 m)-0=4081 J`

And therefore, the average power output of the lifter, using
`t=1.7 s`, is

`P =(W)/(t)= (4081 J)/(1.7 s)=2400 W`