# Inelastic Collision

• Mar 15th 2010, 05:54 PM
elexis10
Inelastic Collision
Heres the question:

two cars collide inelastically and stick together after the collision. Before the collision, the magnitudes of their momenta are http://session.masteringphysics.com/render?var=p_1 and http://session.masteringphysics.com/render?var=p_2. After the collision, what is the magnitude of their combined momentum?

i believe the answer is p1+p2 but am not to sure and would like more input on this
• Mar 15th 2010, 07:08 PM
skeeter
Quote:

Originally Posted by elexis10
Heres the question:

two cars collide inelastically and stick together after the collision. Before the collision, the magnitudes of their momenta are http://session.masteringphysics.com/render?var=p_1 and http://session.masteringphysics.com/render?var=p_2. After the collision, what is the magnitude of their combined momentum?

i believe the answer is p1+p2 but am not to sure and would like more input on this

the key word here is magnitudes, the scalar part (size) of a vector.

momenta are vectors, and as such, are not "added" like scalars unless both are in the same direction.

for example ... the combined momentum after the collision might be zero if the original momenta before the collision were opposite in direction and equal in magnitude.

all you can say is that the combined magnitude of momentum after the collision is less than or equal to the combined magnitude of momentum before the collision.