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

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

since we know the power and the time, we can find the work done:


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:

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