# AS level Mechanics help-pulleys

Hi, I am stuck on a pulleys question, one of the ones where one particle is on the table and one is hanging off it. If the table is described as smooth, and therefore there is no friction, how would I write an equation of motion?
Original post by HBond22
Hi, I am stuck on a pulleys question, one of the ones where one particle is on the table and one is hanging off it. If the table is described as smooth, and therefore there is no friction, how would I write an equation of motion?

Have you drawn a diagram?
Original post by HBond22
Hi, I am stuck on a pulleys question, one of the ones where one particle is on the table and one is hanging off it. If the table is described as smooth, and therefore there is no friction, how would I write an equation of motion?

After drawing a diagram with the forces. Use F=ma on each particle to get the equations of motion.
Original post by bl0bf1sh
Have you drawn a diagram?

yes. Any chance you might be able to tell me how to write the equation for particle P? I know how to do Q, it's just that P isn't acted on by friction as the surface is smooth
Smooth means friction = 0, so it's just T - 0 = 1.5a ... T=1.5a
Original post by vc94
Smooth means friction = 0, so it's just T - 0 = 1.5a ... T=1.5a

Thanks very much!
Original post by vc94
Smooth means friction = 0, so it's just T - 0 = 1.5a ... T=1.5a

Don't give answers - ypu are breaking forum rules - try to get the poster have a go first.
Original post by Muttley79
Don't give answers - ypu are breaking forum rules - try to get the poster have a go first.

Lol! I thought the poster's great diagram was worthy of support! I don't think stating "T=1.5a" is a spoiler; they still have to use their second equation and solve them!
Original post by vc94
Lol! I thought the poster's great diagram was worthy of support! I don't think stating "T=1.5a" is a spoiler; they still have to use their second equation and solve them!

Read the rules before helping again
Original post by HBond22
yes. Any chance you might be able to tell me how to write the equation for particle P? I know how to do Q, it's just that P isn't acted on by friction as the surface is smooth

Technically speaking, you're missing a force there - you've shown the weight of P acting against the table so there needs to be a reaction force ("R") acting upwards to balance it - P isn't burrowing through the table
Original post by Muttley79
Don't give answers - ypu are breaking forum rules - try to get the poster have a go first.

have to say I think you're being a little harsh in this case - the poster did give the F = ma hint first, and once you've got that (which the OP must surely have got imprinted in their head anyway), there really isn't very much else left to write down - I think the OP just need a nudge to get their brain "into gear". I'd say the extra post was borderline helping in this case - more a sort of "look, you've got the difficult bit by yourself, just write down the b*****ing obvious!" I'd be more concerned if the OP had done P's equation and then someone came along and gave them the equation for Q without any hints
Original post by davros
Technically speaking, you're missing a force there - you've shown the weight of P acting against the table so there needs to be a reaction force ("R") acting upwards to balance it - P isn't burrowing through the table

have to say I think you're being a little harsh in this case - the poster did give the F = ma hint first, and once you've got that (which the OP must surely have got imprinted in their head anyway), there really isn't very much else left to write down -

In your opinion. The F=ma was enough - then wait ... I don't agree that they knew that.