Question

a rifle shoots a bullet with a muzzle velocity of 400m/sec at a small a target 400 meter away. the height above the target at which the bullet must be aimed to hit the target is.(take g = ms-2)

Answer 1

uniform motion along x axis and non uniform motion along y axis

Answer 2

If the angle of shooting is α time taken to reach the target
t=400/(400* cosα)=1/cosα
vertical fall in this time = 1/2 * g*t²= 1/2 * 9.8 * 1/cos²α
tanα= vertical fall/distance=(1/2 *9,8*1/cos²α)/400
sinα * cos α =9.8/800
sin2α =2*9.8/800=0.0245
2α= sin inverse of 0.0245=1.404
α=0.702tan
α =0.01225
height of aim = tanα * 400=0.01225*400=4.9 meters above the horizontal.