Question

A bullet of mass $20g$ is found to pass two points $30m$ apart in a time interval of $4$ seconds. Calculate the kinetic energy of the bullet if it moves with constant speed.

Answer 1

from the formula of $speed=\frac{distance}{time}$

thus $speed\left(v\right)=\frac{30}{4}$

thus $v=7.5m/s$

since $K.E=\frac{1}{2}m{v}^2$

$\Rightarrow \frac{1}{2}\times \frac{20}{1000}\times 7.5\times 7.5$(divide by 1000 because mass is in grams)

$\Rightarrow \frac{9}{16}J$

$\Rightarrow 0.5625J$