What does the interaction of a force and distance from a point produce?

• A. Translation
• B. Rotation
• C. Friction
• D. Torque

Answer: (D)

A force applied at some distance from a pivot creates a turning effect. This turning effect is called torque. The size of the torque depends on how far the force is from the pivot (the lever arm) and the direction of the force relative to that lever arm. Mathematically, torque is the cross product of the position vector and the force, so its magnitude is τ = r F sin θ, measured in newton-meters. This is why a longer lever arm makes it easier to rotate an object with the same force, as seen when using a longer wrench. If the force line passes through the pivot, the lever arm is zero and no rotation occurs, even though there might be a net linear force.