Two hockey pucks colliding at 90 degrees and sticking together

[Jeemeli]

Homework Statement

Two hockey pucks collide in a 90 degree angle and stick to each other. What's the speed of the hockey pucks after the collision and in what angle are the pucks moving in.

Homework Equations

m1=0.71kg
m2=0.52kg
v1=1.6m/s
v2=3.8m/s

The Attempt at a Solution

m1v1+m2v2=v(m1+m2)
=0.71kg*1.6m/s+0.52kg*3.8m/s=(0.71kg+0.52kg)*v
=v=(3.1kgm/s)/1.23kg=2.52m/s

 

[kuruman]

Hi Jeemeli and welcome to PF.

Is there something you wish to know about this? If so, please ask.

 

[Jeemeli]

Hi Jeemeli and welcome to PF.

Is there something you wish to know about this? If so, please ask.

My solution was wrong, Id like to know how to get the right answer

 

[jbriggs444]

m1v1+m2v2=v(m1+m2)
=0.71kg*1.6m/s+0.52kg*3.8m/s=(0.71kg+0.52kg)*v

You've gone from a correct formula involving vector velocities and applied it to scalar speeds.

If you walk 1.136 meters north and 1.976 meters east, how far from your starting position will you be as the crow flies?

 

[kuruman]

My solution was wrong, Id like to know how to get the right answer

In short, this is a two-dimensional collision.