Moment of Force

[unknown person]

Is bag strap a moment of force? Ex. the lower the bag is, the heavier? how do you explain it? Do you have a video for clearer explanation, and I can download?

 

Or do you know any examples of moment of force? with videos

 

thank you very much.

[darkenlighten]

A moment is a Force multiplied by the perpendicular distance from the object. So if you consider the shoulders the pivot point and have the weight (force) farther away then yea it might appear to be "heavier" and should act like a moment.

 

Edit for clarity: It won't only appear to be heavier it will cause more of a force.

Edited July 20, 2010 by darkenlighten

[Sisyphus]

No, the longer strap will not make the bag heavier. The downward force of it just hanging there will be identical. Moment of force, i.e. torque, comes into play with "twisting." In the bag example, because it isn't rigid, it always hangs straight down, in the direction of force. You would only get a torque if there were an orthogonal ("sideways") component.

 

So, for example, if he bag was on the end of a rigid stick held out horizontally, it would be exerting more torque if the stick were longer, and it will be more difficult to keep it horizontal. The force here is applied downwards (by gravity), perpendicular to the stick.

[J.C.MacSwell]

No, the longer strap will not make the bag heavier. The downward force of it just hanging there will be identical. Moment of force, i.e. torque, comes into play with "twisting." In the bag example, because it isn't rigid, it always hangs straight down, in the direction of force. You would only get a torque if there were an orthogonal ("sideways") component.

 

So, for example, if he bag was on the end of a rigid stick held out horizontally, it would be exerting more torque if the stick were longer, and it will be more difficult to keep it horizontal. The force here is applied downwards (by gravity), perpendicular to the stick.

 

More mass and closer to the earth?

[darkenlighten]

No, the longer strap will not make the bag heavier. The downward force of it just hanging there will be identical. Moment of force, i.e. torque, comes into play with "twisting." In the bag example, because it isn't rigid, it always hangs straight down, in the direction of force. You would only get a torque if there were an orthogonal ("sideways") component.

 

So, for example, if he bag was on the end of a rigid stick held out horizontally, it would be exerting more torque if the stick were longer, and it will be more difficult to keep it horizontal. The force here is applied downwards (by gravity), perpendicular to the stick.

 

My point was that it can act as a moment, of course when it is hanging straight down, the length will not make it heavier, but as soon as that starts swinging, forces are gonna change. I see it more like a pendulum though.

[Bignose]

More mass and closer to the earth?

 

You are technically correct -- Futurama fans know that that is the best kind of correct. Because an object would be closer to the center of the earth, the gravitational force would be a little stronger. However, I suspect that the wink-y face indicates that we both know that it would be and incredibly tiny amount, and for any and all practical purposes, there is no difference.