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HELP with Mechanics 2 please!

A wire AB 10 metres long is bent into an arc of a circle. It is mounted in a vertical plane so the tangent at B is horizontal and the tangent at A is at 40 degrees to the horizontal, with the level of B below the level of A. A bead of mass 2 grams is threaded on the wire at A and released. Find its speed when it reaches B
a. if the wire is smooth
b. if there is a resistance of constant magnitude 0.004 newtons

The answers are 8.10 and 5.07. There is no diagram that comes with the question.
Reply 1
Is it the diagram that you are finding a problem? Or can you picture the situation, but don't know what to do?
Reply 2
If it's just the diagram, then this should help. You can solve the question by considering the energy changes that go on from A to B.

AB.jpg
Reply 3
Original post by Pangol
If it's just the diagram, then this should help. You can solve the question by considering the energy changes that go on from A to B.

AB.jpg


thanks so much! yeah it was trying to picture the situation that was the problem but that's perfect, thank you.
Edit: Although I'm trying to do energy changes but how can you work out GPE as you don't have the height of A?
(edited 7 years ago)
Original post by e r w
thanks so much! yeah it was trying to picture the situation that was the problem but that's perfect, thank you.
Edit: Although I'm trying to do energy changes but how can you work out GPE as you don't have the height of A?


You can work out the angle that the arc subtends at the centre of the circle. You know the arc length so you can then work out the radius. Then use a triangle to work out the distance of A below the centre of the circle.
Reply 5
Original post by tiny hobbit
You can work out the angle that the arc subtends at the centre of the circle. You know the arc length so you can then work out the radius. Then use a triangle to work out the distance of A below the centre of the circle.


Thanks!

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