- #1

geoffjb

- 165

- 1

Quarterback Fred is going to throw a pass to tight end Doug. Doug is 20 m in front of Fred and running straight away at 6.0 m/s when Fred throws the 500 g football at a 40 degree angle. Doug catches the ball without having to alter his speed and runs for the game-winning touchdown.

How fast did Fred throw the ball?

I am working with the two fundamental kinematics equations:

Code:

```
x = v_ix t
y = v_iy t - 1/2 gt^2
```

(An underscore, _, indicates subscripts. A caret, ^, indicates superscripts.)

Since the final positions of both the receiver and the ball must be identical, I have tried endlessly to modify equations which both involve position (that is, isolating x and then making one formula equal to another). However, some other variable (usually time) always gets in the way of my solving the equation. Any hints which would set me on the right track are appreciated.

Thanks.