# Football tackler

1. Oct 21, 2007

### mathcrzy

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

A 110 kg fullback is running at 4.9 m/s to the east and is stopped in 0.75 s by a head-on tackle by a tackler running due west. Calculate the average force exerted on the tackler.
Magnitude
____N

2. Relevant equations

F=ma

3. The attempt at a solution

F=110*4.9=539N

2. Oct 21, 2007

### hage567

4.9 m/s is velocity, not acceleration. So it doesn't work in that equation. Look up impulse.

3. Oct 21, 2007

### mathcrzy

Impulse=F*deltaT

=(110*4.9)*.75

=404.25

4. Oct 21, 2007

### hage567

You are trying to find F though. You can find impulse by considering the change in momentum of the player. Once you have that, you can then find the average force.

5. Oct 21, 2007

### mathcrzy

would you use the equation (before the collision) M1*V2+M2*V2=M1*V2+M2*V2 (after the collision)

6. Oct 21, 2007

### hage567

That's the right idea, you need to find the change in momentum of the fullback. You were given his initial velocity, so you know the initial momentum. You know he is brought to a stop, so you also know his final momentum.