Question

in the picture below, a bar is set up to rotate about its center (the dark circle). each arrow represents a force that is being applied to the bar. each force has the same magnitude
using the center as the pivot point, answer the following questions.
a.) which force has no lever arm?
○ b
○ a
○ d
○ c

Explanation:

Step1: Recall the definition of lever arm

The lever arm (or moment arm) is the perpendicular distance from the pivot point to the line of action of the force.

Step2: Analyze each force

• For force \(A\), the line of action of the force passes through the pivot point. The perpendicular distance from the pivot (center) to the line of action of force \(A\) is \(d = 0\).
• For force \(B\), there is a non - zero perpendicular distance from the pivot to the line of action of the force.
• For force \(C\), there is a non - zero perpendicular distance from the pivot to the line of action of the force.
• For force \(D\), there is a non - zero perpendicular distance from the pivot to the line of action of the force (the perpendicular distance can be found by dropping a perpendicular from the pivot to the line of action of force \(D\)).

Answer:

A. A