Conservation of Energy and Mechanical Advantage (4A) Practice Test

A clinician uses a non-ideal block-and-tackle to lift a $15\ \text{kg}$ rehabilitation weight stack by $0.40\ \text{m}$. The rope is pulled $1.6\ \text{m}$ with an average force of $50\ \text{N}$. Which statement is most consistent with energy conservation and the distinction between mechanical advantage and efficiency? (Use $g=10\ \text{m/s}^2$.)

A $0.50\ \text{kg}$ instrument is lowered at constant speed by a motorized winch through $2.0\ \text{m}$. The motor acts as a brake and delivers $6\ \text{J}$ of electrical energy to a resistor during the descent. Which prediction best aligns with conservation of energy? (Use $g=10\ \text{m/s}^2$.)