I The Correlation of Pressure and Torque in Rotational Motion

AI Thread Summary
The pressure exerted on a screwdriver does not directly determine the torque during rotation; rather, it is the grip and friction that matter. Sufficient axial force is necessary to prevent the screwdriver from slipping out of the screw head, and this force depends on the torque and screw head profile. A worn screwdriver requires more axial force to achieve the same torque due to decreased effectiveness. The grip's tightness increases friction, which in turn enhances torque application. Ultimately, understanding torque performance relies more on force and friction than on pressure.
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TL;DR Summary
Does pressure determine the magnitude of torque?
When you hold a screwdriver with your hand, a pressure is exerted on it. Does the pressure you exert determine the magnitude of torque in rotating the screwdriver?
 
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No, only to the extent that you need to grip the screwdriver hard enough to not slip wheen you turn it.
 
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Robeurer said:
When you hold a screwdriver with your hand, a pressure is exerted on it. Does the pressure you exert determine the magnitude of torque in rotating the screwdriver?
Depends what the grip looks like.

For a smooth solid of revolution grip, the pressure only determines the maximally possible torque, which comes from frictional forces.

But most grips don't look like that, so the local normal forces from pressure do have tangential components which contribute to axial torque.
 
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Welcome to PF.

It is force, not pressure, that determines the performance of a screwdriver. Pressure is force per unit area. Area is not relevant to the forces that are applied while using a screwdriver.

You must apply sufficient axial force, to prevent the screwdriver from being rejected by, and disengaging from the screw head. The axial force required, will depend on the torque being applied, and the head profile of the screw. A worn screwdriver will require greater axial force to deliver the same torque.

You must apply sufficient radial grip force, to prevent the handle sliding with friction against your hand. Your grip of the handle limits the torque that can be applied.
 
Robeurer said:
TL;DR Summary: Does pressure determine the magnitude of torque?

When you hold a screwdriver with your hand, a pressure is exerted on it. Does the pressure you exert determine the magnitude of torque in rotating the screwdriver?
The tighter your grip on the handle, the greater the friction force exerted on the handle. The greater the friction force the greater the torque. The concept of pressure is not needed to understand this.
 

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