The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Mechanics homework!!!!

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!!
Reply 1
Avatar for Actaeon
Actaeon
11
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 :smile:
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.
Reply 2
Avatar for Sykesy1
Sykesy1
OP
I've drawn the diagram but not sure how to find the coefficient of friction?
Reply 3
Avatar for Actaeon
Actaeon
11
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 F=μRF = \mu R you can replace the friction in this equation with μR\mu R.

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

Then consider F=ma for each particle :smile:
Reply 4
Avatar for Sykesy1
Sykesy1
OP
okay thanks I'll have a go
Reply 5
Avatar for Sykesy1
Sykesy1
OP
What two equations would I use?

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you