Question

A boy weighting $40kg$ carries a box weighting $20kg$ to the top of a building $15m$ high in $25$ seconds. Calculate the power. ($g=10m/s^2$)

Answer 1

Weight of boy $=40kg$

Weight of box $=20kg$

Total weight $\left(mg\right)=60\times 10=600N$

Height $\left(h\right)=15m$

Time $\left(t\right)=25s$

Increase in potential energy $=mgh$

Increase in potential energy $=600\times 15$

Increase in potential energy $=9000J$

We know that enrgy is equal to work done and vice versa

Therefore Work Done $\left(W\right)=9000J$

Power $=\frac{W}{t}$

Power $=\frac{9000}{25}$

Power $=360J{s}^{-1}$

Power $=360W$