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    Hi

    I am not sure how to answer questions 2 and 3.
    Is a turning effect the same as a moment. I know that a moment is the force multiplied by the distance but is it the amount of energy needed to turn something?
    I got 140N for the first question and I initially thought it would be the same for question 2 but then I saw that question 3 required calculating the force.

    Thank you
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    (Original post by musicangel)
    Hi

    I am not sure how to answer questions 2 and 3.
    Is a turning effect the same as a moment. I know that a moment is the force multiplied by the distance but is it the amount of energy needed to turn something?
    I got 140N for the first question and I initially thought it would be the same for question 2 but then I saw that question 3 required calculating the force.

    Thank you
    The moment is the turning effect of a force, they're the same thing. If the 30N load is in the hand I'm not sure how you got 140N for the first question, it should just be force * distance (In meters), so the units should be Nm.

    2 is also looking for an moment (Nm) but 3 is just looking for a force (N), the units can help you figure out what you're supposed to do between 2 and 3.
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    (Original post by __Adam__)
    The moment is the turning effect of a force, they're the same thing. If the 30N load is in the hand I'm not sure how you got 140N for the first question, it should just be force * distance (In meters), so the units should be Nm.

    2 is also looking for an moment (Nm) but 3 is just looking for a force (N), the units can help you figure out what you're supposed to do between 2 and 3.
    Thank you for your help! With a moment, what is the value showing - is it how much force you need to turn something? If so, how much would it turn?
    Tthe load should be 10N and I misread question 1. Would it be 280Nm?
    How would question 2 be different as wouldn't the arm be balanced in the calculation for 1?

    Thank you
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    (Original post by musicangel)
    Thank you for your help! With a moment, what is the value showing - is it how much force you need to turn something? If so, how much would it turn?
    Tthe load should be 10N and I misread question 1. Would it be 280Nm?
    How would question 2 be different as wouldn't the arm be balanced in the calculation for 1?

    Thank you
    When you find the moment of a force (or the turning effect/torque. They're all pretty much the same thing), it can be used to find out if a system is in equilibrium or not, like in this question. It also comes up whenever you're looking at rotational motion.

    You could call the moment a "turning force" I guess, just instead of pulling or pushing something, you're rotating it instead. When you apply a force to something that's on a pivot, it starts to rotate. The moment's just a measure of the ability of a force to make something rotate.

    If the 30N load is supposed to be 10N, I'd just multiply that 10N by the 0.3m distance for the moment. What did you do to get 280Nm? As for 2, for the system to be in equilibrium (balanced) the moment caused by the load on the hand should be equal but opposite to the moment caused by the effort. If both moments weren't the same, the system would start to rotate and it wouldn't be in equilibrium.

    It's like dealing with forces, if you push something equally hard with 2 forces in opposite directions, it won't move. If you have equal moments in opposite directions, it won't rotate.


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    (Original post by __Adam__)
    When you find the moment of a force (or the turning effect/torque. They're all pretty much the same thing), it can be used to find out if a system is in equilibrium or not, like in this question. It also comes up whenever you're looking at rotational motion.

    You could call the moment a "turning force" I guess, just instead of pulling or pushing something, you're rotating it instead. When you apply a force to something that's on a pivot, it starts to rotate. The moment's just a measure of the ability of a force to make something rotate.

    If the 30N load is supposed to be 10N, I'd just multiply that 10N by the 0.3m distance for the moment. What did you do to get 280Nm? As for 2, for the system to be in equilibrium (balanced) the moment caused by the load on the hand should be equal but opposite to the moment caused by the effort. If both moments weren't the same, the system would start to rotate and it wouldn't be in equilibrium.

    It's like dealing with forces, if you push something equally hard with 2 forces in opposite directions, it won't move. If you have equal moments in opposite directions, it won't rotate.


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    Thank you so much for your help.
    I was wondering with this question if the centre of mass would be on the fulcrum as that is where it is balanced?
    For ii) I do not understand what the question is asking - is it saying t draw an arrow from the centre of mass downwards? For the calculation, would I do 30x0.8=24 and then multiply that by 2 as it is balanced on both sides?

    Thank you
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    (Original post by musicangel)
    Thank you so much for your help.
    I was wondering with this question if the centre of mass would be on the fulcrum as that is where it is balanced?
    For ii) I do not understand what the question is asking - is it saying t draw an arrow from the centre of mass downwards? For the calculation, would I do 30x0.8=24 and then multiply that by 2 as it is balanced on both sides?

    Thank you
    The centre of gravity is the point of an object where you can consider gravity to be acting, so it's like a force coming from that point acting straight down. If that's above a fulcrum then there's no moment caused by it since F*d = F*0 = 0 Nm. As long as there's no resultant moment caused by other forces then the object will be balanced.

    Can a ruler be balanced by putting a fulcrum off to the left like that without adding more forces? If not then the centre of mass can't be there. Where do you put a fulcrum under a ruler to balance it without applying more forces? That will tell you where the centre of gravity is and if you have a ruler you can test it yourself.

    For ii) yes, the weight of the rule acts through the centre of gravity. As for the calculation, remember that distance is in meters. Also until you get the centre of gravity in the right place, you can't get the correct moment since you don't know d for the moment caused by the centre of mass.
 
 
 
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