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# M1 - a couple of questions watch

1. Could anyone help me with a couple of M1 questions?

Firstly, Part iii A) and B)

I've got them right, but I've just assumed friction changes direction from what it was in part i/ii. How do I know that friction changes direction (in both parts) without knowing the value of T??

Then this one:

4 part i. The mark scheme is not helpful at all here.

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2. (Original post by indigorain)
I've got them right, but I've just assumed friction changes direction from what it was in part i/ii. How do I know that friction changes direction (in both parts) without knowing the value of T??
Because the 3N force is still being applied and without T it's in limiting equilibrium. If T is now applied and it's again in limiting equilibrium, it must be on the verge of moving in the opposite direction, and friction is thus in the opposite direction to what it was before.

4 part i. The mark scheme is not helpful at all here.
You need to show that for all values of 'e', the velocity of Q is greater than zero, i.e. it has changed direction.
3. Alright lets upload part 2, ill do part 1 in a moment. Btw this was my M1 exam

EDIT: Part 1 was answered by ghost walker.
4. (Original post by indigorain)
Then this one:

4 part i. The mark scheme is not helpful at all here.

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I am 100% sure this is right as I got 72/72 on this paper.

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5. (Original post by ghostwalker)
You need to show that for all values of 'e', the velocity of Q is greater than zero, i.e. it has changed direction.
This is M1, all collisions are perfectly elastic. They have not learnt about coefficient of restitution, that is M2
6. Thank you very much, everyone!

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