If an object is falling with constant velocity, what can be said about its net force?

• A. Zero
• B. Unbalanced forces
• C. Net force equals mass times acceleration
• D. Unknown

Answer: (A)

Constant velocity means there is no change in motion, so acceleration is zero. Newton’s second law tells us that net force equals mass times acceleration; with acceleration zero, the net force must be zero. In this situation gravity pulls downward while air resistance pushes upward, and at terminal velocity these forces balance, canceling each other to give zero net force. That’s why the object continues moving at the same speed.

Unbalanced forces would cause a change in velocity, so that isn’t correct. The statement “net force equals mass times acceleration” is true in general, but here it leads to zero net force because acceleration is zero. “Unknown” isn’t necessary since we can deduce the net force from the constant velocity.