The term mutual velocity, can be described as?

1. Nov 4, 2008

JohnnyB212

The term "mutual" velocity, can be described as?

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

A 110 kg tackler moving at 3.0 m/s meets head-on (and tackles) a 95 kg halfback moving at 7.5 m/s. What will be their mutual velocity in meters/second immediately after the collision?

2. Relevant equations

m1 = 110kg
V01 = 3.0 m/s
m2 = 95 kg
V02 = 7.5 m/s
V1f = Final Velocity of the 110 kg tackler
V2f = Final Velocity of halfback

V1f = ((m1-m2)/(m1+m2))V01

V2f = ((2m1)/(m1+m2))V01

3. The attempt at a solution

V1f = 1.68
V2f = 24.68

Am I correct for both? How would I determine the mutual velocity? I noticed V02 wasnt used, so i'm a little confused, any help would be appreciated, thanks.

2. Nov 4, 2008

Staff: Mentor

Re: The term "mutual" velocity, can be described as?

"Mutual" in the sense of "shared in common". The two players stick together after the collision and thus have the same velocity.

Redo your calculations with that in mind.

3. Nov 4, 2008

JohnnyB212

Re: The term "mutual" velocity, can be described as?

Was the equation correct?

4. Nov 4, 2008

JohnnyB212

Re: The term "mutual" velocity, can be described as?

Oh! I caught myself on the V1f, which is actually .5897

Still, confused about the mutual portion. How are you to determine the common similarities of two completely different numbers?

5. Nov 4, 2008

Staff: Mentor

Re: The term "mutual" velocity, can be described as?

No.

Instead of plugging into some formula (which doesn't apply to this situation), why not just apply conservation of momentum?

The collision is perfectly inelastic (they collide and move together). Hint: Direction matters--they are headed toward each other.