How do you find the initial speed?

[Hannah :)]

2586 kg van runs into the back of a 824 kg compact car at rest. They move off together at 8.5 m/s. Assuming the friction with the road can be negligible, find the initial speed of the van.

i don't even know where to start :/

 

[rock.freak667]

Since they are colliding, what quantity do you know is conserved in collisions?

 

[Hannah :)]

umm i don't know?

 

[rock.freak667]

umm i don't know?

Do you know anything about what mass*velocity gives?

 

[Hannah :)]

yea it gives momentum

 

[rock.freak667]

yea it gives momentum

So in a collision, is momentum conserved or not?