# Torque? Rotation it has the Word Pivot

• Kalie
In summary, the conversation discusses how to calculate the amount of force the biceps must exert to hold a ball with the forearm parallel to the floor, with the forearm being modeled as a 2.50 kg, 32-cm-long "beam" that pivots at the elbow and is supported by the biceps. The solution involves determining the net moment and taking into account the distributed load of the forearm.
Kalie
Torque? Rotation it has the Word Pivot...

A forearm can be modeled as a 2.50 kg, 32-cm-long "beam" that pivots at the elbow and is supported by the biceps.
http://session.masteringphysics.com/problemAsset/1001007/10/knight_Figure_13_58.jpg
How much force must the biceps exert to hold a 430 g ball with the forearm parallel to the floor?
Okay So I have no clue how to aproach. I'm thinking torque=rFsin theta and solve for F...but I don't knwo how to do that

Anyone want to give me a small clue to start this?

Oh yeah when you look at the picture is r=2.5 cm...?

Thanks

Is 2.5cm the distance to where the bicep muscle attaches to the horizontal forearm beam?

If so, draw the free body diagram, with the tension vector up the bicep muscle broken down into its vertical and horizontal components.

The picture makes it clear that the biceps are attached at 2.5 cm from the elbow (pivot).

This is a matter of determining the net moment. Also realize that the forearm "can be modeled as a 2.50 kg, 32-cm-long "beam" that pivots at the elbow and is supported by the biceps."

One must know how to take the moment of the forearm, which is a distributed load. Hint: think center of mass.

## 1. What is torque?

Torque is a measure of the rotational force applied to an object. It is the product of the force applied and the distance from the pivot point to the point where the force is applied.

## 2. How is torque related to rotation?

Torque is directly related to rotation. When a force is applied to an object, it creates a torque that causes the object to rotate around its pivot point.

## 3. What is a pivot point?

A pivot point, also known as a fulcrum, is the fixed point around which an object rotates. It is the point at which the object experiences no torque.

## 4. Can torque be negative?

Yes, torque can be negative. This means that the direction of rotation is opposite to the direction of the applied force. It is often represented by a negative sign in equations.

## 5. How is torque measured?

Torque is typically measured in units of Newton-meters (N*m) in the metric system or foot-pounds (ft-lb) in the imperial system. It can be calculated using the formula: torque = force x distance.

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