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## QuestionPhysicsClass 11

A projectivle is fired form the top of a 40 m hnigh cliff with an initial speed of 50 m/s at an unknown angle. Find its speed when it hits the ground.

$${h}={40}{m},{u}={50}\frac{{m}}{{\sec{}}}$$
let the speed be v when it strikes the ground.
Applying law of conservation of energy,
$${m}{g}{h}+\frac{{1}}{{2}}\mu^{{2}}=\frac{{1}}{{2}}{m}{v}^{{2}}$$
$$\rightarrow{10}\times{40}+{\left(\frac{{1}}{{2}}\right)}\times{2500}=\frac{{1}}{{2}}{v}^{{2}}$$
$$\rightarrow{v}^{{2}}={3300}$$
$$\rightarrow{v}={57.4}\frac{{m}}{{\sec{=}}}{58}\frac{{m}}{{\sec{}}}$$