# Projectile Motion Ball Hurl Question

1. Mar 26, 2014

### yoyo16

1. The problem statement, all variables and given/known data

If you can hurl a ball so that its initial speed is 30m/s, what is the widest river you can throw it across?

2. Relevant equations
The range equations,
t=2(vi)(sintheta)/g

d=visin2theta/g

3. The attempt at a solution

I know you have to use components so what I got what Vx=30sintheta and Vy=30costheta

I don't know what to do next or how to sub it in because there isn't a angle given . Can someone please help me. Thanks

2. Mar 26, 2014

### rock.freak667

You have your formula for the range as

$$d = \frac{v_i sin2 \theta}{g}$$

For you to throw it at the max range, you'd need to throw it such that your angle θ and hence sin2θ is maximum.

What is the maximum value that sin2θ can be?

3. Mar 26, 2014

### Rellek

Forgot a square!

4. Mar 26, 2014

### yoyo16

The angle must be 45 degrees to get max range right?

5. Mar 26, 2014

### yoyo16

Oh ok, I got the answer. Thanks so much !!