What is the speed of two railroad cars after they collide?
September 21st, 2007 | by cars |
finding.4ever asked:
A railroad car of ams m is moving at speed v when it collides with a second railroad car of mas M which is at rest. The two cars lock together instantaneously and move along the track.
A railroad car of ams m is moving at speed v when it collides with a second railroad car of mas M which is at rest. The two cars lock together instantaneously and move along the track.
What is the speeed of the cars immediatly after the collision?
How would you find it?
CARMEN
2 Responses to “What is the speed of two railroad cars after they collide?”
By cathaychris on Sep 23, 2007 | Reply
This problem involves momentum conservation.
p = p’, which means the momentum before is equal to the momentum afterwards.
To calculate the momentum of the system (which always includes both cars) before the collision, it is p= m * v + M * V (where v is the speed of the car in motion; V is the speed of the car at rest). Because V = 0, the momentum prior to the collision is simply m*v = mv.
Afterwards, the mass of the system will be (m+M). To find the momentum, it’s (m+M)*v2 (which is just some velocity).
Setting the two momentums equal,
mv = (m+M)*v2
Solving for v2,
v2 = mv/(m+M)
By Kevin on Sep 23, 2007 | Reply
v1 - speed of car 1 before collision
m = mass of car 1
M = mass of car 2
v2 = speed of car 2 = 0
v3 = speed of both cars after collision
mv1 +Mv2 = (m+M)v3
v3 = m/(m+M)