Question

A bullet of mass 10g is fired horizontally with velocity 100ms¹ from a rifle situated at a height 50m above the ground.if bullet reaches ground with a velocity 500ms¹,the work done against air resistance in trajectory of bullet is g=10ms²​

Answer 1

Answer:

See below.

Explanation:

Total initial energy of the bullet,

$\begin{aligned}Ei=mgh+\dfrac {mv^{2}}{2}\\ =\left( 0.01\right) \left[ \left( 10\right) \left( 50\right) +\dfrac {\left( 100\right) ^{2}}{2}\right] \\ =55J\end{aligned}$

Reaching the ground, the bullet has only kinetic energy which is the total final energy,

$\begin{aligned}E_{f}=\dfrac {1}{2}\left( 0.01\right) \left( 500\right) ^{2}\\ =12\cdot 5\times 100\\ =1250J\end{aligned}$

The difference between them is the work done against air resistance,

$\begin{aligned}W=55-1250\\ =-1195J\end{aligned}$