Moments/torque in relation to laws of motion

In summary, torque (tau) is equal to force (F) multiplied by distance (d), while force (F) is equal to mass (m) multiplied by acceleration (a). In the case of a rod with a pivot, the force applied on one end is transferred to the other end through the attractive forces holding the atoms/molecules of the rod together. When the applied force is too strong, the bonds may break, causing the rod to fail.
  • #1
Kinhew93
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I've just started learning about torque, and understand that tau=Fd, but wondered how this relates to F=ma.

For example if there is a rod with a pivot in the middle (say a nail), when one end is pushed down, why does the other end move up? Where is the force that causes the end to move up coming from?

thanks :)
 
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  • #2
The force that moves the other end is the attractive forces holding the atoms/molecules of the rod together. The force applied on one end is transferred to the other via these bonds. Hence, if you strike the end of the rod hard enough you will apply too much acceleration for the bonds to hold and it will break, while the other end barely moves at all.
 
  • #3
Kinhew93 said:
I've just started learning about torque, and understand that tau=Fd, but wondered how this relates to F=ma.

The "equivalent" expressions would be...

Force = mass * acceleration

Torque = moment of inertia * angular acceleration

For example if there is a rod with a pivot in the middle (say a nail), when one end is pushed down, why does the other end move up? Where is the force that causes the end to move up coming from?

Take a look at the forces in a beam. The top of the beam is in tension and the bottom of the beam is in compression. If these forces are unbalanced by the application of a new force the beam will accelerate (eg it will start to rotate or if already rotating it will rotate faster).

and as Drakkith said..if the forces are too large the beam will fail.
 

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1. What is a moment/torque?

A moment or torque is a measure of the force that causes an object to rotate around an axis. It is the product of the force applied to an object and the distance from the axis of rotation.

2. How is moment/torque related to Newton's first law of motion?

According to Newton's first law of motion, an object at rest will remain at rest and an object in motion will continue moving in a straight line at a constant speed unless acted upon by an external force. In the case of a rotating object, this external force is the moment or torque that causes the object to rotate.

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

While both a moment/torque and a force can cause an object to move, they act in different ways. A force is a push or pull applied to an object in a specific direction, whereas a moment/torque causes an object to rotate around an axis. Additionally, a moment/torque has both a magnitude and a direction, while a force only has a magnitude.

4. How does moment/torque affect an object's rotational motion?

Moment/torque is directly proportional to an object's rotational acceleration, meaning the larger the moment/torque, the greater the rotational acceleration. This can be seen in the equation τ = Iα, where τ is the moment/torque, I is the moment of inertia, and α is the angular acceleration.

5. What are some real-life examples of moments/torque in relation to laws of motion?

Moments/torque can be seen in many everyday situations. For example, when opening a door, the moment/torque is exerted on the door handle, causing it to rotate around its hinges. In sports such as baseball or golf, the moment/torque from swinging a bat or club causes the ball to rotate and move in a particular direction. Another example is when using a wrench to tighten a bolt, the moment/torque is applied to the bolt, causing it to rotate and tighten.

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