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?

neither is correct

Explanation:

Given data

object is equilibrium

center of mass = zero

external forces = zero

to find out

which one correct mass is zero or external forces is zero

solution

here we know object is equilibrium if  net torques about center of mass = 0 and other is um of external forces= zero

we can say that from this given data external force and torque about the axis is zero

net force about any point of body is zero but net torque is not 0

so neither is correct in both

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.