Realistically, why is it that momentum is not always conserved in a system.?

Question

For instance, in the physics lab we did with 2 carts colliding in elastic and inelastic collisions, the total change in momentum was not zero. What momentum are we not accounting for and why is the effect not noticeable?

For elastic collisions we had magnets on the bumpers of the carts that collided and for inelastic, we had velcro.

Answer 1

Steve is quite right that momentum is never lost to friction. If momentum seems to have been "lost" in your experiment, it really means that the momentum got transferred to something else.

The momentum of things like carts usually gets transferred through contact.

If the cart bumps or rubs against anything, there is likely to be some momentum transferred between the cart, and the other thing that it bumped or rubbed against.

If the "other thing" is very massive, then the other thing's velocity will change very little during the momentum transfer. In fact, you might not notice any change at all in the other thing's motion.

So ask yourself this: During the experiment, did your carts bump or rub against anything that was very massive? Or something that was _fastened_ to something that was very massive? (Something like, say, a planet?)

Answer 2

In real life there is no collision which is "perfectly elastic"

Due to this some energy is lost (change in momentum) mostly in form of heat.

Secondly there is no surface which is frictionless, so some energy is always lost in friction.

If you get the final sum of momentums less than the initial then the above explanation answers. However, if you are getting final momentum more than the initial, there is some measurement error.

Answer 3

First of all, how exactly did you get an elastic collision in the lab - between two carts?

Secondly there are experimental errors due to measurements. The measurements may not be accurate. And also the measurements may not have been JUST before and after impact. If you wait too long after impact, the velocities slow down because of rolling friction and other factors. So these may significantly compromise the accuracy of your measurements.

Answer 4

The basic answer to this question is friction. However there are many other ways energy is lost. In a perfect system no energy is lost to heat and sound in the collision, and to friction (heat) of the surfaces. However in the real world these factors must be considered.
As kinetic energy is proportional to mass times velocity and this energy is decreased by the factors I discussed previously, the mass and velocity are decreased.
As momentum= mass*velocity the momentum is therefore decreased.
I hope this answers you question.

Answer 5

i might consider Steve, yet might upload the stipulation that the gadget could desire to be isentropic; in different words, if there are warmth losses via friction, and so on in the gadget, then i does no longer assume the guidelines of momentum conservation to act as predicted via the classic sort. extra: Lisa - confident, that's an incredible occasion. Or an ice skater spinning. quite something that strikes that's interior our adventure does no longer strictly obey the momentum conservation rules. There are continually losses. in any different case, we'd be waiting to make a perpetual action device. Entropy has a tendency to improve over the years, meaning issues do no longer stay neat and tidy.

Answer 6

Experimental error.
Momentum Is ALWAYS conserved.
Believe it.
BTW, Momentum is NOT lost to friction; energy IS lost. They are 2 completely different things frequently confused.