# physics

posted by on .

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 - ,

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 - ,

I wonder if Count Iblis transposed 34 to 43? Check my thinking.

• physics - ,

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 - ,

xhat and y hat are unit direction vectors, of magnitude 1. Thus 12xhat is 12 in the x direction.