Question

A ball is kicked at an angle of 35 with the ground . What is the initial velocity of the ball so that it hits a target that is 30 metres away at a height of 1.8 metres?

Answer 1

Given:

$\theta=35^{\circ}$

$x=30\:\rm m$

$y=1.8\:\rm m$

The trajectory equation of a ball

$$y=x\tan\theta-\frac{gx^2}{2v_0^2\cos^2\theta}$$

We get

$$1.8=21-6572/v_0^2$$

Finally,

$$v_0=\sqrt{342}=19\:\rm m/s$$