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Momentum

I have difficulties understanding energy and momentum collisions. Infact, collisions as a whole. Can anyone help? I have a test in a few days....
Reply 1
Avatar for dream123
dream123
OP
2
anyone? ^^^
Reply 2
Avatar for vVPiKaVv
vVPiKaVv
1
Not sure what exactly you are asking...but generally..

Inelastic collisions => momentum conserved
Elastic collisions => momentum and energy conserved

Completely inelastic collisions can be identified if the 2 colliding particles stick to each other and move off with the same velocity.

Generally, to solve these type of questions...try conservation of momentum first because it always works and is simpler as there is no squared term. Do take note that momentum is a vector and you must be clear about the signs of the velocities involved.

Alternatively, for elastic collisions, it can be derived that the relative speed of separation = relative speed of approach (derived from conservation of momentum and energy), which can be applied easily.
vVPiKaVv
Not sure what exactly you are asking...but generally..

Inelastic collisions => momentum conserved
Elastic collisions => momentum and energy conserved

Completely inelastic collisions can be identified if the 2 colliding particles stick to each other and move off with the same velocity.

Generally, to solve these type of questions...try conservation of momentum first because it always works and is simpler as there is no squared term. Do take note that momentum is a vector and you must be clear about the signs of the velocities involved.

Alternatively, for elastic collisions, it can be derived that the relative speed of separation = relative speed of approach (derived from conservation of momentum and energy), which can be applied easily.


yup, p=mv and k.e.=0.5mv^2
therefore p= square root of (2k.e./m)
I can make up a small tutorial for you if you think it would be useful...

Just leave a reply on this thread and I'll check back tomorrow and an get it done by tomorrow late afternoon i would think.
Reply 5
Avatar for -G-a-v-
-G-a-v-
16
In a nutshell...

There's two main types of collision: elastic and inelastic.

Momentum is conserved in both types of collision.
Kinetic energy is also conserved in elastic collisions, but not in inelastic ones.

Momentum is the product of the body's mass and velocity.
Impulse is the change in momentum
Force is defined as the rate of change of momentum.

Conservation of momentum means that the total initial momentum = the total final momentum.

When doing collision questions, it helps to have a diagram showing the velocities before and after the collision. Remember if the bodies are moving in opposite directions, the velocity vector for one of them will be negative (depending on which way you take to be positive, usually to the right i.e. the same way as numbers increase on the positive x-axis)

If youre revising for a test, the best way to prepare is to do lots of questions, then come on here with specific questions. If you can be clear about where the problem lies, we'll be able to help you more effectively :smile:
Reply 6
Avatar for Drummy
Drummy
10
a collision is when 2 or more objects bang into each other

does this help?
Reply 7
Avatar for Dadeyemi
Dadeyemi
13
Drummy
a collision is when 2 or more objects bang into each other

does this help?


most helpful comment of all :smile:

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