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# AS Physics - Help with moments question watch

1. Hey guys, hoping you can help me with this question on moments. I'm struggling to understand the whole principle right now.

Would post the Q here, but contains diagrams.

Anyway, it's question (6)(a)(ii).

(6)(c)(ii) also gave me a bit of trouble, but I think I figured it out with a little help from the mark scheme.

Thanks for any help
2. What exactly have you done for both parts?
Or are you just generally stuck?
3. Moment = force x perpendicular distance
Anticlockwise moments are positive, clockwise ones are negative.
Total moment = Sum of anticlockwise and clockwise moments.

Also: anticlockwise 4N force, perpendicular distance is x
clockwise 4N force, perpendicular distance is (x + 3.0cm)
4. Okay thanks guys Probably should have put a bit of work down.

1)

So, the clockwise moment would be: 4.0 x (0.03 + x)
And the anticlockwise moment would be: 4x

Right?

So do we add these together to find the total moment?
5. Oh wait, if you meant clockwise moments are positive, then I think I've got it.

Clockwise = 4 x (0.03 + x) = 0.12 + 4x

Therefore, total moment = 0.12 + 4x - 4x which equals 0.12.

Significance being it is the same value as the torque!
6. (Original post by NoNamedUser)
Oh wait, if you meant clockwise moments are positive, then I think I've got it.

Clockwise = 4 x (0.03 + x) = 0.12 + 4x

Therefore, total moment = 0.12 + 4x - 4x which equals 0.12.

Significance being it is the same value as the torque!
correct
7. the moment of a couple is equal to the force times the perpendicular distance

so the solution is
Moment=Fd
= 4x(3x10^-2)
= 0.12Nm
8. (Original post by NoNamedUser)
Oh wait, if you meant clockwise moments are positive, then I think I've got it.

Clockwise = 4 x (0.03 + x) = 0.12 + 4x

Therefore, total moment = 0.12 + 4x - 4x which equals 0.12.

Significance being it is the same value as the torque!
Indeed correct.
9. Thanks guys

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