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# Momentum And Force IGCSE Question HELP! watch

1. Hey. Just studying and came across a question I'm not too confident about...

A trolley of mass 0.20kg travelling at 1.5 m/s to the right collides with a trolley of mass 0.30kg moving in the opposite direction at 0.5 m/s.

A) Calculate the total momentum before the collision.

B) Calculate the velocity of the trolleys after the impact if they move off together.

I know the answers but need an explanation on how to work this out properly.
Also any one willing to tutor me/ answer and explain a bunch of questions, I would be eternally grateful to.
2. inbox me
3. (Original post by CarleyFarley)
Hey. Just studying and came across a question I'm not too confident about...

A trolley of mass 0.20kg travelling at 1.5 m/s to the right collides with a trolley of mass 0.30kg moving in the opposite direction at 0.5 m/s.

A) Calculate the total momentum before the collision.

B) Calculate the velocity of the trolleys after the impact if they move off together.

I know the answers but need an explanation on how to work this out properly.
Also any one willing to tutor me/ answer and explain a bunch of questions, I would be eternally grateful to.

With momentum questions remember that momentum is always conserved, meaning that the momentum before an impact is equal to the momentum after an impact. I was taught to show this in an easy equation form:

(M1 x U1) + (M2 x U2) = (M1 x V1) + (M2 x V2)

where M1 is the mass of the first object and M2 is the mass of the second object, U1 is the initial velocity of the first object and U2 the initial velocity of the second object and V1 is the velocity of object 1 after impact and V2 is the velocity after the impact of object 2.

Remember that velocity is a vector quantity so take a direction to be positive when doing your workings (otherwise you'll use incorrect signs and get an incorrect answer!).

In any momentum question like this you will have 3 of the 4 pieces of information and need to work out the last piece, usually the velocity of one of the objects (or both if they coalesce) after the collision.

when formatted like this the equation is really easy to use in my opinion and allows you to work out your solution in one go, keep practising and good luck!

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