Conservation of Momentum with Collisions

AI Thread Summary
In a collision between a diesel engine and a freight car, the engine is eight times heavier and moves at 3 km/h, while the freight car moves at 2 km/h. To find the final velocity of the combined system after the collision, the conservation of momentum principle is applied. The equation used is V = (md * vd + mf * vf) / (md + mf), where md is the mass of the diesel engine and mf is the mass of the freight car. Simplifying the equation by substituting the mass of the engine as 8m leads to a final velocity calculation. The conclusion suggests that the final velocity of the linked engine and car combination is 5 km/h.
Sadiebunkins
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Homework Statement



A diesel engine weighs 8 times as much as a freight car. This diesel engine, moving on a horizontal track at 3 km/h, crashes into the freight car (which was moving at 2 km/h in the same direction). What is the velocity, in km/h, of the now linked together engine/car combination? You may assume no numerical values not given.

Homework Equations



V= mdvd + mfvf over M or md + mf

The sub d is for diesel engine
The sub f is for freight car

The Attempt at a Solution


I am not really sure is the m's cancel and all that is left with is the v's. If so the final velocity would be 5 km/h
 
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Try calling the mass of the car m and then write the mass of the engine as 8m. You might be able to see what ends up canceling afterward.
 

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