Which statement best describes how to calculate torque in a lever?

Which statement best describes how to calculate torque in a lever?

• A. The force magnitude and the lever arm length (perpendicular distance) determine torque.
• B. Torque depends only on force magnitude.
• C. Torque depends only on lever arm length.
• D. Torque is unrelated to force direction.

Answer: (A)

Torque is the turning effect a force has about a pivot. The size of that turning effect comes from two main factors: how hard you push (the force magnitude) and how far from the pivot you apply that push (the lever arm). The angle between the force and the lever matters too, because only the part of the force that acts perpendicular to the lever actually causes rotation. The relationship is torque = r F sin(theta), where r is the distance from the pivot to where the force is applied, F is the force magnitude, and theta is the angle between the force and the lever. If you push perpendicular to the lever, torque is maximal (theta = 90°, sin = 1). If you push along the lever, torque is zero (theta = 0°, sin = 0). This shows why both the force and the lever arm are essential in determining torque.

Torque is the turning effect a force has about a pivot. The size of that turning effect comes from two main factors: how hard you push (the force magnitude) and how far from the pivot you apply that push (the lever arm). The angle between the force and the lever matters too, because only the part of the force that acts perpendicular to the lever actually causes rotation. The relationship is torque = r F sin(theta), where r is the distance from the pivot to where the force is applied, F is the force magnitude, and theta is the angle between the force and the lever. If you push perpendicular to the lever, torque is maximal (theta = 90°, sin = 1). If you push along the lever, torque is zero (theta = 0°, sin = 0). This shows why both the force and the lever arm are essential in determining torque.