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# Mechanics homework!!!! watch

1. I need help on this question:
A particle A of mass 5kg rests on a rough plane inclined at 30 degrees to the horizontal. A string attached to A lies along a line of greatest slope of the plane and passed over a smooth pulley at the top of the plane. A particle B of mass 6kg hangs vertically from the string 1m above a horizontal plane. The system is released from rest with the string taut. If B takes 2 seconds to reach the horizontal plane, find the coefficient of friction between A and the inclined plane. Find also the total distance that A moves up the plane, assuming A does not reach the pulley ?

THANKYOU FOR ANY HELP!!
2. Firstly, draw a force-body diagram, showing all the forces (friction, weight, tension, normal reaction etc.) on each body and the relevant angles.
Then try and form two equations, by considering F=ma on each particle. You can then combine these to get a single equation dependent on the friction coefficient and the acceleration, but you can find the acceleration of the system by finding the acceleration of B. So you can solve for the friction coefficient
For the second part, you have to consider firstly how far A moves when it is under tension (while B is falling) and how far it moves when the rope becomes slack (after B hits the ground). Again, a force-body diagram should help here.
3. I've drawn the diagram but not sure how to find the coefficient of friction?
4. (Original post by Sykesy1)
I've drawn the diagram but not sure how to find the coefficient of friction?
Well, look at body A and resolve parallel and perpendicular to the slope.

Perpendicular to the slope, you can form an equation based on the normal reaction and the weight. Parallel to the slope, you can form one based on friction and the tension in the rope. As you can replace the friction in this equation with .

Remember you can find R from your equation resolving perpendicular to the slope.

Then consider F=ma for each particle
5. okay thanks I'll have a go
6. What two equations would I use?

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