Collision equation help needed

I need help solving this, my exam is on Monday so this is kind of urgent

Hi @sarah.roycroft,

You probably already know that the equation for calculating momentum is:

momentum = mass x velocity

Using that, can you calculate the momentum of the red car before the collision?
What would the momentum of the blue car be?

You should be able to add both of these, giving you the total momentum before the collision.

According to the law of conservation of momentum, we know the total momentum before, will equal the total momentum after the collision (in the absence of any external forces). So we now know the total momentum after.

We can work out the momentum of the blue car after the collision, given the values in the question.

Then we can subtract the blue cars momentum from the total momentum, this must be the momentum of the red car.

So we know the mass of the red car, and it’s momentum. Rearrange the equation to find the velocity.

GIve that a shot and see how you get on. If you’re still struggling, let me know and I can walk you through the calculations.

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Is the final velocity of the red car v=0.54m/s?
Because that’s what I got using what you said

Nice work. That looks correct to me. I would always encourage you to include the direction (even though it is shown in the question), as stating the correct direction may make a difference in terms of the grade awarded for that question.

ok thank you so much!!

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