you throw a rock up into the air as hard as you can. it stays in the air for 8 seconds. what was the velocity of the rock when you threw it?

Respuesta :

Answer:

39.2 m/s

Step-by-step explanation:

Let a = 9.8 m/s^2, t = 8 sec, find the initial velocity v

After time t, the rock hit the ground, so the height h = 0

Use h = vt - at^2/2 = 0

v = at/2 = 9.8 * 8/2 = 39.2 m/s