# Momemuntum of bodies at right angles

## Homework Statement

Hi
Can someone help with this problem.
2 particles of mass 30g and 40g respectively both travel at a speed of 35m/s in directions at right angles. The 2 particles collide and stick together. Calculate their speed after impact.

## Homework Equations

MaVa + MbVb =(Ma + Mb)v
v= common velocity

## The Attempt at a Solution

I am not sure how to start. Solving the total momentum before and total momentum after gives the original speed. I then resolved the respective velocities. But that means I got my final value without consideration of the masses! Finally, I resolved the masses into forces, but still didnt get anywhere. Where I am going wrong? Please advice

rock.freak667
Homework Helper

## Homework Equations

MaVa + MbVb =(Ma + Mb)v
v= common velocity

Since they impact at right angles, that means that you have momentum in two directions, x and y.

So for the x-direction you would have

MaVax + MbVbx =(Ma + Mb)vx

and Vbx=0.

Do the same with the momentum in the y-direction and then you know the resultant velocity is given by

$$v=\sqrt{v_x^2+v_y^2}$$

Since they impact at right angles, that means that you have momentum in two directions, x and y.

So for the x-direction you would have

MaVax + MbVbx =(Ma + Mb)vx

and Vbx=0.

Do the same with the momentum in the y-direction and then you know the resultant velocity is given by

$$v=\sqrt{v_x^2+v_y^2}$$
Thanks a lot.