Question

A ball is thrown straight upward with a velocity of 24m/s How much time passes before the ball strikes the ground? Disregard air resistance.

Answer 1

Knowing that when you throw something in the air, the speed will be 0m/s.
The acceleration due to gravity is 9.8m/s^2.

v2=0
v1=24
a=9.8

The formula is:
v2=v1+a(t)
v2-v1/a=t
0-24/9.8
24m/s/9.8m/s^2=t (You can choose which direction is positive and negative)
2.45s=t
t=2.45*2s (Since you calculate both going up and down)
t=4.9s