Question

A stone is launched from the ground, at a 70° angle, with an initial velocity of 120 m/s.

Once you determine when the stone hits the ground, which equation would you use to find its final horizontal distance?
A) x = 41t
B) x = 60t
C) x = 84.7t
D) x = 120t

Answer 1

x = 41t is correct

Step-by-step explanation:

The horizontal component of the rock's velocity is 120(cos70°). You would plug the time the rock landed into this equation.

Answer 2

A) x = 41t
The classic equation for distance is velocity multiplied by time. And unfortunately, all of your available options have the form of that equation. In fact, the only difference between any of the equations is what looks to be velocity. And in order to solve the problem initially, you need to divide the velocity vector into a vertical velocity vector and a horizontal velocity vector. And the horizontal velocity vector is simply the cosine of the angle multiplied by the total velocity. So H = 120*cos(70) = 120*0.34202 = 41.04242 So the horizontal velocity is about 41 m/s. Looking at the available options, only "A" even comes close.