# Homework Help: Collision physics homework help

1. Mar 12, 2005

### tandoorichicken

A car heading north collides at an intersection with a truck heading east. If they lock togethr and travel at 28 m/s at 38° north of east just after the collision, how fast was the car initially traveling? Assume that the vehicles have the same mass.

Does this problem not depend on how fast the truck was traveling also?

2. Mar 12, 2005

### physicsCU

It does, but I think you can solve for it using dynamics once you have the right momentum equation set up.

I am not sure what you would do to set up for it though, but i think you would start with (m1 + m2)*vfx = m1*vix + m2 *v2x,

and do another one for the y-direction. Since mass is the same, I'd assume that final velocity in each direction is the initials in that direction added together, but i am not sure on that.

Not sure of the dynamics equation either, but I'd try that.

3. Mar 12, 2005

### gd

If I'm not mistaken, then the momentum in the y direction is going to be equal before and after the collision, so you can set up an equation like
M*vcar = 2M*28sin38

2M on the right side because the vehicles are the same mass... the M's cancel and you can solve for vcar.

Last edited: Mar 12, 2005