Question

A body is dropped from height $8m$. After striking the surface it rises to $6m$, what is the fractional loss in kinetic energy during impact? Assuming the frictional resistance to be negligible.

• A. $1/2$
• B. $1/4$
• C. $1/6$
• D. $1/8$

Answer 1

The correct option is B $1/4$

The correct option is B.

Given,

$H_1=8m$

$H_2=6m$

The height from which the body falls gives it a potential energy which converts to kinetic energy as the body falls down. When the body finally hits the ground, all the potential energy was converted to kinetic energy. If we assume the mass of body as M kg, then

Mgh = (final kinetic energy)

80M = (final K.E.) Since $g=10m/s^2$

Since the ball got $6m$ height,

So, $KE=\frac{6}{8}\times 100$

$=75\%$

Thus the energy loss when the object was bounced back,

$(100-75)\%=25\%$

$\frac{1}{4}$