Question

A student fires a cannonball vertically upwards. The cannonball returns to the ground after a 6.00s flight. Determine all unknowns and answer the following questions. Neglect drag and the initial height and horizontal motion of the cannonball. Use regular metric units (ie. meters).

Answer 1

Given:

$t=6\:\rm s$

$g=9.8\:\rm m/s^2$

Unknown:

$v_0,\; h_{\max}.$

The time of motion to the up

$$t^*=t/2=3\:\rm s$$

The initial velocity

$$v_0=gt^*=9.8*3=29.4\:\rm m/s$$

The maximum height

$$h_{\max}=\frac{v_0^2}{2g}=\frac{29.4^2}{2*9.8}=44.1\:\rm m$$