Torque Physics Example 4

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Example 4

medium
A door (1 m1 \text{ m} wide) requires 50 N m50 \text{ N m} of torque to open. What force must be applied at the edge of the door, perpendicular to it?

Solution

  1. 1
    Use τ=rF\tau = rF with r=1 mr = 1 \text{ m} (distance from hinge to edge).
  2. 2
    F=τr=501=50 NF = \frac{\tau}{r} = \frac{50}{1} = 50 \text{ N}

Answer

F=50 NF = 50 \text{ N}
Applying force at the edge of a door (maximum distance from the hinge) requires the least force to produce the needed torque. Pushing near the hinge requires much more force.

About Torque

The rotational equivalent of force; a measure of how much a force tends to cause an object to rotate about an axis.

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