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 01-08-2007, 11:56 PM #1 Junior Member   Join Date: May 2006 Posts: 167 Physics Momentum Problem i need help fast!! An 11900 lb railroad car traveling at 6.8 ft/s couples with a stationary car of 6690 lb. The acceleration of gravity is 32 ft/s^2. a. What is their velocity after the collision? b. What impulse did the first car recieve? Answer in units of lb s. Note lb s.. is basically lbs times seconds.... in case u were wondering. any tips on how to get the answer for b. i think im jus screwing up on units.. i kinda need to turn it in, in like an hr.. so plz help!! thanks Reply
 01-11-2007, 05:17 PM #2 Junior Member   Join Date: Sep 2006 Posts: 59 Once you get the right answer for the first, the second should be trivial. Impulse is the change in momentum, so simply take M(second car)*V(final), and reverse it. Or find the difference in the momentum of the first car initially and final. Reply

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