Question

A projectile is fired from the top of a $40m$ hight cliff with an initial speed of $50m/s$ at an unknown angle. Find its speed when it hits the ground.

Answer 1

Given data,

Height of the cliff, $h=40m$

nitial speed of the projectile, $u=50m/s$

Let the projectile hit the ground with velocity ${}^{\prime }{v}^{\prime }.$

Applying the law of conservation of energy,

$mgh+\frac{1}{2}m{u}^2=\frac{1}{2}m{v}^2$

$10\times 40+\frac{1}{2}\times 2500=\frac{1}{2}{v}^2$

$v^2=3300$

$v=57.4m/s=58m/s$

The projectile hits the ground with a speed of $58m/s$