Physics

Problem

A uniform meterstick is pivoted at its 50\,cm mark and is held horizontal. Three forces act on the stick as listed below. • 5\,N downward at the 20\,cm mark • 5\,N upward at the 80\,cm mark • 10\,N downward at the 50\,cm mark Which force produces zero torque about the pivot? a) The

5\,\text N

upward force at the

80\,\text{cm}

mark b) The

10\,\text N

downward force at the

50\,\text{cm}

mark c) The

5\,\text N

downward force at the

20\,\text{cm}

mark d) All three forces produce non-zero torque

Intuitive explanation

This problem is about recognizing that torque depends on where a force acts relative to the pivot, not just its magnitude. The key insight is that torque equals force times perpendicular distance from the pivot—so any force applied at the pivot point itself has zero moment arm and produces no torque, no matter how strong it is. Check which force acts at the 50 cm mark.

Intuitive explanation

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