The horizontal velocity is constant. (Ignore air resistance.) Recall from your study of trigonometry that if you release a rock at a speed v in a direction that makes an angle α with the horizontal, then the initial vertical velocity vv and the horizontal velocity vh are given by

Question

vv = vsinα and vh = vcosα

You shoot a rifle at an angle of 42 degrees. The bullet leaves your rifle at a height of 6 feet and a speed of 810 feet per second.

It hits the ground after how many seconds at a distance of how many feet?

Answer 1

Recall that the vertical height h is

h(t) = 6 + (810 sin42)t - 16t^2

so, just solve for t when h=0.