# Homework Help: The range of a ball

1. Jan 19, 2004

### DR33

a tennis ball is thrown from the ground. 3 secs later, Vx = 15 m/s (horizontal). Determine the range.

2. Jan 19, 2004

### DR33

Answer is 90.0m.. I just dont know how to get to it??

3. Jan 19, 2004

### NateTG

If the horizontal velocity is 15 m/s and the ball spends 3 seconds in the air, then the total distance it travels is 45 meters.

Distance=rate*time.

If it takes 3 seconds to reach the peak of it's flight, then it goes 90m.

4. Jan 19, 2004

### DR33

Thank so much..
I just made a fool of myself when I think about it again :p

L8er

5. Jan 19, 2004

### NateTG

You asked about the angle of impact. It's easier to figure out the peak altitude by using:
$$\frac{1}{2}at^2$$

And realizing that the ball hits the top halfway through the fight.

If you want to find the angle of impact, the easiest option is that it's the same as the angle of launch. Alternatively, you can use the inverse tangent and the x and y velocities at impact.

6. Jan 26, 2004

### Julian Solos

You must have written the problem incorrectly. As it was written, it didn't have enough information.

"Vx = 15 m/s (horizontal)" was misleading. Vx is always horizontal, if we assume the x-axis is horizontal, and it's always 15 m/s if we are allowed to ignore air resistance.