Physics Question

Question

A rock is thrown at 12 m/s at an angle of 60 degrees above horizonal. It takes 4 seconds for the stone to fall on the ground.

A. How high does the rock rise?

B. How long is it in the air if it falls to the elevation at which it was thrown?

C. How far from the thrower does the rock land?

Answer 1

The vertical velocity at the beginning is 12 * sin (60) = 12 * sqrt(3) /2 ~ 10.4 m/s

The horizontal one is 12 * cos (60) = 6 m/s

So it takes 10.4 / 9.8 ~ 1.06 sec to reach to the top (i.e. where v_up = 0).

The height it reaches 1/2 * 9.8 * t^2 ~ 5.5 m (A)

It takes the same time to fall to the same elevation, so the total time in the air when it falls to the same elevation is 2.12 sec. (B)

The horizontal distance it travels = 6 m/s * 4 sec = 24 m. (C)