William B. answered • 08/20/19

For Math, Physics, and anything else with equations...

If you're shooting it from the ground, you can just find the total time in the air and divide by two.

We start with the equation y_{f = (-1/2)gt}^{2} + v_{0}t + y_{0}.

Plugging in our values, we get 0 = (-1/2)(9.81)t^{2} + 23.4t.

This can then be factored, and we can solve for each factor: 0 = t [ (-1/2)(9.81)t + 23.4 ]

The 't' outside just gives us zero, which is the initial time (i.e. the beginning of the problem), so we can ignore it.

Solving for the other factor, we get:

(-1/2)(9.81)t + 23.4 = 0

==> -4.905t + 23.4 = 0

==> -4.905t = -23.4

==> t = 4.77 seconds.

Half of this is 2.39 seconds. Tada!