Posted by **Ty** on Thursday, December 13, 2007 at 5:54pm.

Hi! I have a problem for physics homework and I though I knew how to solve it but apparently it is wrong, please help!

'Two cars, one of mass 1000 kg, and the second of mass 2400 kg, are moving at right angles to each other when they collide and stick together. The initial velocity of the first car is 11 m/s in the positive x direction and that of the second car is 19 m/s in the positive y direction.

What is the magnitude of the velocity of the wreckage of the two crs immediately after the collision? Answer in units of m/s"

I did (1000*11)+(2400*19)=3400*v3

is that correct?

- physics -
**Count Iblis**, Thursday, December 13, 2007 at 6:10pm
You forgot to include the directions of the speeds. The correct equation is:

1000*11 x-hat +2400*19 y-hat=3400*v3

v3 = 110/43 x-hat +24*19/43 y-hat

The magnitude of v3 is thus:

sqrt[(110/43 )^2 + (24*19/43 )^2]

- physics -
**Ty**, Thursday, December 13, 2007 at 6:23pm
so does 10.908 sound right?

Also, ( just so I know for future problem) what is x-hat and y-hat (we just started 2d collisions so I am sorry if this is very obvious)

- physics -
**bobpursley**, Thursday, December 13, 2007 at 8:23pm
xhat and y hat are unit direction vectors, of magnitude 1. Thus 12xhat is 12 in the x direction.

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