A mason worker throws the bricks to a height of 10m, at which the bricks reach with a velocity of 6ms^–1. The percentage of energy he is wasting is nearly (g = 10ms^–2)

Given,

h= 10m

v = 6m/s

Increase in potential energy $=mgh=m\times 10\times 10=100m$

Kinetic energy at the top point = $\frac{1}{2}m{v}^2=\frac{m\times 36}{2}=18m$

Total work done,

$W=PE+KE$

$W=100m+18m = 118m$

Due to this KE, the brick doesn't need to travel any further, therefore the velocity will be wasted, and the percentage of wasted energy will be

$\frac{KE}{W}\times 100\%=15.25\%$

Hence the correct answer is 15%.