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Moments equilibrium uniform rod q

When choosing the point to take moments at can it be any point or the point that has a force attached so like when you have a uniform rod with two supports attached at C and D for eg do you need to take moments at C or D or any point is fine?
Reply 1
Avatar for ThomH97
ThomH97
21
Any point is fine, but it's easier if you choose it at a point where a force is acting because then that force's moment will be zero. It's fewer terms to mess about with in the equations.
Reply 2
Avatar for Sidd1
Sidd1
OP
13
Original post by ThomH97
Any point is fine, but it's easier if you choose it at a point where a force is acting because then that force's moment will be zero. It's fewer terms to mess about with in the equations.

Oh okay thank you:smile:
Reply 3
Avatar for Sidd1
Sidd1
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Also, I have another question where it asks where you should place a support on a broom so that it will balance horizontally. How would you know where the support should be placed like which side of the uniform rod?? In the mark scheme they put it on the side near where there is already a weight of 5.5g. The question says also that the broomstick is modelled as a uniform rod of length 130cm and mass 5g and the broomhead is a particle of mass 5.5g. Why is the support placed towards the weight of 5.5g?
the weight at the end is a little heavier so to make the moments equal the distance to the end needs to be a little shorter
Reply 5
Avatar for ThomH97
ThomH97
21
Think about how you could balance a broom in your hand. If you held it in the middle the head would just tip and you'd have to try quite hard to keep it level. As you move your hand toward the head, it'll be easier to balance it, and you could even balance it on one finger if you were precise enough.

They are modelling the broom handle as a uniform rod, and the head is the 5.5g.
Reply 6
Avatar for Sidd1
Sidd1
OP
13
Original post by Meowstic
the weight at the end is a little heavier so to make the moments equal the distance to the end needs to be a little shorter

I'm sorry but I don't get that:frown:
Reply 7
Avatar for Sidd1
Sidd1
OP
13
Original post by ThomH97
Think about how you could balance a broom in your hand. If you held it in the middle the head would just tip and you'd have to try quite hard to keep it level. As you move your hand toward the head, it'll be easier to balance it, and you could even balance it on one finger if you were precise enough.

They are modelling the broom handle as a uniform rod, and the head is the 5.5g.

Oh I know that but I'm saying why did they place the support towards the head ?
Reply 8
Avatar for ThomH97
ThomH97
21
Original post by Sidd1
Oh I know that but I'm saying why did they place the support towards the head ?


They're putting the support where it will balance the broom. Or you could say they're putting the broom on the support where it will balance.

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