Question

the picture below shows two people lifting a heavy log. which of the two people is supporting the greatest weight? a. alice b. bob c. they support the same weight

Explanation:

Step1: Consider the principle of moments

Take the center of the log (the hole) as the pivot. Let the weight of the log be \(W\). Let the distance from Alice to the pivot be \(d_{A}\) and from Bob to the pivot be \(d_{B}\). Assume the force exerted by Alice is \(F_{A}\) and by Bob is \(F_{B}\). For rotational equilibrium, \(F_{A}\times d_{A}=F_{B}\times d_{B}\). Since \(d_{A}F_{B}\) (because \(W = F_{A}+F_{B}\) and from \(F_{A}\times d_{A}=F_{B}\times d_{B}\), \(F_{A}=\frac{d_{B}}{d_{A}}F_{B}\) with \(\frac{d_{B}}{d_{A}}> 1\)).

Answer:

A. Alice