Wednesday, 7 June 2017

newtonian mechanics - Why does Conservation of Momentum fails because of friction?




I did this experiment in my lab. We had two cars with wheel connected by a string. One car has a spring that can be triggered by a switch at the top of the car. (Frictionless surface and light string$


We press it and the two cars explode and we measure of the distance travelled by each car and the mass of each.


We then figured out from the ratio of each car's mass-distance product, that the momentum is conservation because the ratio is always 1. (Assuming time for each car to stop is same)


But for the last trial, we flipped a car to creat friction (no wheel). Then the ratio is zero anymore, meaning no conservation of momentum.


My teacher told me to find the force of friction acting on the car , I need to find the difference in the momentum of the two cars and use the time the car with friction takes to stop figure out the force. Why does this way of finding out the force works?


Did frictional force acting on each cart create the same impulse in each cart? Why/not ?




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