Which indicates a balanced force on an object at rest or moving at constant velocity?

• A. Net force equals zero
• B. Net force equals mass times acceleration
• C. Net force equals velocity
• D. Net force equals momentum

Answer: (A)

The main idea is that motion changes only when there’s an unbalanced force. If the net force on an object is zero, there’s no unbalanced push, so its motion stays the same: an object at rest stays at rest, and an object moving with constant velocity continues to move with the same speed and direction. This is why zero net force describes a balanced situation: acceleration is zero, and there’s no change in motion.

The other statements don’t describe this balance. F_net = m a is the general relation from Newton’s second law, which tells us how force and acceleration are connected, but it doesn’t specify that the net force must be zero in this situation. Net force equal to velocity would mix two different quantities, which isn’t a valid relation. Net force equal to momentum likewise confuses force with momentum, which are distinct concepts.