Is the force on a moment/torque carried?

  • Thread starter Illusion3
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In summary: explained that the closer you are to a hinge, the smaller the torque will be because it becomes harder to apply the same amount of force.
  • #1
Illusion3
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Hello,

I had an interesting thought about how moments work, and if the force is carried.

If I am pushing on the handle of a door, say 10 metres away from the pivot, a force of 10 Newtons, the total moment would be 100nm.

Does this mean that at every point of the door, half way for instance, the moment will be the same? Say for instance at the point 5 metres from the pivot, can you say that the moment at that point is also 100nm, and thus the force must be 50 Newtons? This makes no sense, as the force applied 1cm from the pivot would be 1000 Newtons.

Albeit what my teacher told me, I believe that if you half the distance from where you push, the force will also be halved, and thus the moment quartered, although I have no mathematical proof.

Thanks for your help!
 
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  • #2
Hello Illusion3! :smile:

i'm not sure i follow you :confused:

if the amount of force is fixed, then the torque gets less as you get nearer the hinge …

the door is harder to push, in the sense that it moves slower for the same force

alternatively, if you push with the same moment, then the amount of force you need is increased as you get nearer the hinge
 
  • #3
Thanks for your reply,

I think my question is a little confusing. Please look at the following attachment that should display the diagram about my question.

In other words, the diagram shows that if I apply a force at the top, obviously half way in the middle there is also a moment, although my hand doesn't push at that area. What would the force be half way in the middle?
 

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  • Moment.bmp
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  • #4
Illusion3 said:
In other words, the diagram shows that if I apply a force at the top, obviously half way in the middle there is also a moment, although my hand doesn't push at that area. What would the force be half way in the middle?

Sorry, I have no idea what you mean. :confused:

A moment of what about what?
 
  • #5
Easy.

If you apply 10 Newtons 10 meters away from the hinge, it's 100 Nm (since you do 10x10)

If you apply 10 Newtons 5 meters away from, it'd be 50 Nm that you're applying (since you do 10x5)

So, the closer you get to the hinge, provided you're applying a constant force, the moment will decrease. That's why you never push a door to open it close to the hinge.


If you want the moment to equal 100 5 meters away from the door, you'd need to apply 20 Newtons (since you do 20x5)

Hope that helps,

-Dory
 

1. What is the difference between force and moment/torque?

Force and moment/torque are both physical quantities that describe the interaction between two objects. Force is a vector quantity that describes the push or pull on an object, while moment/torque is a vector quantity that describes the rotational force on an object.

2. How is the force on a moment/torque calculated?

The force on a moment/torque is calculated using the equation F = r x M, where F is the force, r is the distance from the point of rotation to the point where the force is applied, and M is the moment/torque.

3. What are some real-life examples of moments/torques?

Some real-life examples of moments/torques include twisting a doorknob, using a wrench to tighten a bolt, and turning a steering wheel while driving a car. These all involve applying a force at a distance from the point of rotation.

4. Can a moment/torque exist without a force?

No, a moment/torque cannot exist without a force. A moment/torque is a result of a force being applied at a distance from the point of rotation. Without the force, there would be no rotational effect.

5. How does the direction of the moment/torque affect its effect?

The direction of the moment/torque affects its effect by determining the direction of the resulting rotation. If the moment/torque is applied in the same direction as the rotation, it will cause the object to rotate faster. If the moment/torque is applied in the opposite direction, it will cause the object to slow down or stop rotating.

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