Angie says that an object is in equilibrium if the net torques about the center of mass is zero. Robbie says that an object is in equilibrium if the sum of external forces is zero. Which one, if either, is correct?
A) Both are correct: an object is in equilibrium if either condition holds.
B) Neither is correct: both conditions must hold simultaneously.
C) Neither is correct: the net external force and the net external torque about any axis must be zero.
D) Neither is correct: an object is in equilibrium only if its velocity is zero in all coordinate systems.
E) Both are correct: if the sum of the external forces is zero, the net torque about any axis is automatically zero, and vice versa.

Question

Quizplus · Accepted Answer

For an object to be in equilibrium, both the sum of external forces and the net external torque about any axis must be zero. Therefore, neither Angie nor Robbie is completely correct. Additionally, statement D does not accurately describe equilibrium, and statement E is not necessarily true for all cases.

Angie Says That an Object Is in Equilibrium If the Net