The power P is the amount of work W done in a certain amount of time t
[tex]P= \frac{W}{t} [/tex]
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 [tex]m=260 kg[/tex] between its final location (height h=1.60 m) and its initial location (the floor, h=0). This potential energy difference is
[tex]\Delta U = mgh_f-mgh_0 =(260 kg)(9.81 m/s^2)(1.60 m)-0=4081 J[/tex]
And therefore, the average power output of the lifter, using [tex]t=1.7 s[/tex], is
[tex]P =\frac{W}{t}= \frac{4081 J}{1.7 s}=2400 W [/tex]
