Question

A weightlifter expends 294 w of power lifting a weight to a height of 2 m in 10 seconds. what mass has he lifted?

Answer 1

The power of the weightlifter is equal to the ratio between the work done by it and the time taken:

`P= (W)/(t)`
since we know the power and the time, we can find the work done:

`W=Pt=(294 W)(10 s)=2940 J`

For the work-energy theorem, this work done by the lifter is equal to the gravitational potential energy gained by the mass, which is given by:

`U=mg \Delta h`
where m is the mass and
`\Delta h` is the increase in height. Rearranging the formula and using W=U, we can find the mass:

`m= (U)/(g\Delta h)= (2940 J)/((9.81 m/s^2)(2 m))=149.8 kg`