How Fast Was the Truck Moving Before the Collision?

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SUMMARY

The discussion focuses on a physics problem involving a collision between a 900 kg car traveling east at 12 m/s and a 2200 kg truck moving north. The conservation of momentum equations are applied, specifically MV = P, where the initial momentum of both vehicles must equal the final momentum after the collision. The user attempts to solve for the truck's initial velocity (vi) but encounters difficulties in isolating vi from the equation 10800 + 2220vi = 3100vf. The solution requires considering the vector nature of momentum and breaking it into components.

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Homework Statement


Two vehicles stick together as a result of the collison. If the 900 kg car was initially at 12 m/s east, then with what speed was the 2200 kg truck traveling north if they move off together in a direction equally north and east.


Homework Equations


MV = P
Pi = Pf
(M1)vi + (M2)vi = Mvf


The Attempt at a Solution


I worked out the equation, but I got lost after that.
(900)(12) + (2220)(vi) = (900+2200)(vf)
10800 + 2220vi = 3100vf

How would I find vi from that equation?
 
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welcome to pf!

hi twistedcolors! welcome to pf! :smile:
twistedcolors said:
(M1)vi + (M2)vi = Mvf

(900)(12) + (2220)(vi) = (900+2200)(vf)

nooo :redface:

https://www.physicsforums.com/library.php?do=view_item&itemid=53" is a vector, and the conservation of momentum is a vector equation …

you need to take components in a particular direction :wink:

try again! :smile:
 
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