Comments on: What is the speed of two railroad cars after they collide? http://www.cargearusa.com/blog/what-is-the-speed-of-two-railroad-cars-after-they-collide/ Mon, 21 May 2012 18:44:47 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Kevin http://www.cargearusa.com/blog/what-is-the-speed-of-two-railroad-cars-after-they-collide/comment-page-1/#comment-482 Kevin Wed, 04 Feb 2009 21:52:15 +0000 http://www.cargearusa.com/blog/what-is-the-speed-of-two-railroad-cars-after-they-collide/#comment-482 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) 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)

]]> By: cathaychris http://www.cargearusa.com/blog/what-is-the-speed-of-two-railroad-cars-after-they-collide/comment-page-1/#comment-481 cathaychris Sun, 01 Feb 2009 10:43:11 +0000 http://www.cargearusa.com/blog/what-is-the-speed-of-two-railroad-cars-after-they-collide/#comment-481 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) 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)

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