In physics, equilibrium is when the net force on an object does what? A) Is greater than zero B) Equals gravity C) None of these D) Equals zero

What this question is really asking

Equilibrium is about whether forces cancel out so the object has no acceleration. So you want the choice that matches Newton’s first and second laws.

Linking equilibrium to Newton’s laws

From Newton’s second law, $$F_{\text{net}} = ma$$ If an object is in equilibrium, then its acceleration is zero, $a=0$. That means: $$F_{\text{net}} = m(0) = 0$$ So the net force must be zero.

Checking each option quickly

• A) Is greater than zero: If $F_{\text{net}} > 0$, then $a>0$, so the object is accelerating, not in equilibrium.
• B) Equals gravity: Gravity can be one of the forces, but equilibrium depends on the sum of all forces. Often gravity is balanced by a normal force or tension, so $F_{\text{net}}=0$ even though gravity is not zero.
• C) None of these: Incorrect because one option is correct.
• D) Equals zero: Correct because forces balance and there is no acceleration.

Example to picture it

A book resting on a table has gravity downward ($mg$) and the table’s normal force upward ($N$). In equilibrium, $N = mg$, so the net force is $N - mg = 0$.