Question

An object of Mass $40kg$ is raised to a height of $5m$ above the ground what is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half way down.

Answer 1

Given :

Mass of the object $M=40kg$

Height upto which it is raised $h=5$ m

Potential energy $P.E=Mgh$

$P.E=40\times 10\times 5=2000J$

Let its kinetic energy be $E_k$ when it is half way down i.e $h^{\prime }=\frac{h}{2}$

According to conservation of energy,

$K.E_i+P.E_i=K.E_f+P.E_f$

$0+2000=E_k+Mg\frac{h}{2}$

$\therefore$ $2000=E_k+40\times 10\times \frac{5}{2}$

$⟹E_k=1000J$