Answer
(a) We would need to load 85 crates in one minute.
(b) We would need to load 23 crates in one minute.
Work Step by Step
We can find the energy required to lift one crate a vertical distance of 0.90 m above the ground.
$E = mgh = (30~kg)(9.80~m/s^2)(0.90~m)$
$E = 264.6~J$
(a) $0.50~hp = (0.50~hp)(746~W/hp) = 373~W$
For the average power output to equal 373 W, the number of crates per second is $\frac{373~W}{264.6~J}$.
We can find the required number of crates per minute.
$\frac{373~W}{264.6~J}\times 60~s = 85~crates$
We would need to load 85 crates in one minute.
(b) For the average power output to equal 100 W, the number of crates per second is $\frac{100~W}{264.6~J}$.
We can find the required number of crates per minute.
$\frac{100~W}{264.6~J}\times 60~s = 23~crates$
We would need to load 23 crates in one minute.
