Question

A 15-kilowatt motor is used to hoist an 800 kg bucket of concrete to the twentieth floor of a building under construction to height of 90 m. assuming no energy is lost along the process, how much time is required?

Answer 1

Upward force needed =bucket's weight =(mg)

800$×$ 9.8=7,840N

Power available (P)=1.0 × 15×10³W=1.5×10⁴W

Since P=$\frac{W} {t} =\frac{Fs} {t}$

Therefore ;$t=\frac{7,840×90} {1.5×10^4}$

=470.4 seconds