Question

The motor of a overhead crane raises a load of 810kg at a velocity of 0.4m/s. the efficiency is 80 percent.

What is the output power?

Answer 1

Force experienced by crane, $F=mg=810\times9.8=7938\space N$

Velocity of load, $v=0.4\space m/s$

Input Power $=F\times v=3175.2\space W$

Efficiency of crane, $\eta=80\%$

Output Power $=\dfrac{Input\space Power}{\eta}=\dfrac{3175.2}{0.80}=3969 \space W$