Question

A machine-gun mounted on a height bordering a lake is fired in a horizontal direction. The muzzle velocity of the bullets is v₀ . What will be the velocity of the bullets when they strike the water if the machine-gun is at a height h above the water?

Answer 1

Answer: 

Explanation:

The bullet has two simultaneous motions: uniform motion along the horizontal at a constant velocity equal to the initial velocity v0 , and that of a free fall in the vertical direction. These two motions are composed to give a resultant motion along a parabola. We assume that B is the point where the bullet hits

the water (Fig.); BC is the velocity vector of the bullet when it strikes the water, BD is the horizontal component of the vector v and equals v_x, and BE is the vertical component v_y . Since v_x = v₀ and v²_y= 2gh, then the velocity of the bullet when it hits the water is