projectiles

Projectiles

A bullet is to be fired with a speed of 1000 m/sec to hit a target 200 m away on a horizontal level If g=10 m/sec² At what height (h) the gun should be hold to fire and hit the target?

200 m

h

For a projectile, time taken to cover the horizontal distance = time taken to cover the vertical height as free fall

 ie time taken to cover 200 m = time for free falling h m

 time =distance / speed ( for uniform motion in the horizontal direction)

 t=200 ÷ 1000 =0.2 sec

 by  Newtons equations of motion

 h=ut+½gt²

 u=0 (^. . ^. free fall)

 h=0+½ ×10 × 0.04= 0.2 m

 ie the gun must hold at a height of 20 cm above the target

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