A crane uses a block and tackle to life a 25 kN boulder to a height of 26 m.
a. how much work is done on the stone? put your answer in scientific notation.
b. if the work is done in 15s, what is the power output in watts and in horsepower?
W=mgh = 25000•26=650000=6.5•10^5 J.
P=W/t=6.5•10^5/15 =4.33•10^4 W =58.87 hp
(1hp=735.4 W; 1 W=0.001356 hp)