Question

A mason worker throws the bricks to a height of $10 m$, at which the bricks reach with a velocity of $6 ms^{-1}$. The percentage of energy he is nearly ($g = 10 ms^{-2}$)
a) $15 \%$
b) $18 \%$
c) $220 \%$
d) $36 \%$

Answer 1

Hint : When an object is in action, it holds energy that is named kinetic energy. The potential energy held by the object is the power present in it by its position, which means potential energy is deposited energy in the object when work is performed on the object, but there is no difference in the velocity or the object's speed.

Complete step-by-step solution:
Height to which bricks throws, $h = 10 m$
Velocity of brick, $v = 6 ms^{-1}$
Potential Energy, $PE = mgh$
$\implies PE = m \times 10 \times 10 = 100m$
Kinetic Energy, $KE = \dfrac{1}{2} m v^{2}$
$\implies KE = \dfrac{1}{2} m 6^{2} = 18m$
Total work done by the man is equal to the sum of kinetic energy and potential energy.
$W = KE +PE$
$\implies W = 18m + 100m$
$\implies W = 118m$
Brick reaches with the velocity of $6 m s^{-1}$, there is wastage of energy due to kinetic energy.
Percentage of energy will be $\dfrac{KE}{W} \times 100$.
$\implies \dfrac{18m}{118m} \times 100 = 15.25 \%$.
The percentage of energy is nearly about $15 \%$.
Option (a) is correct.

Note: Work and energy are nearly related to each other. Work can be described as the transference of energy. For two objects, the work performed is represented as transferring energy from the primary object to the next object. Also, energy is determined as the ability to do work. Work is supposed to be done by a force when an object undergoing displacement parallels the force's line of action.