If a 5 kg block on a frictionless surface experiences a net force of 0 N, what is its acceleration?

• A. 0 m/s^2
• B. 5 m/s^2
• C. 10 m/s^2
• D. 1 m/s^2

Answer: (A)

The main idea is that acceleration comes from the net force acting on something: a = F_net / m. If the net force is zero, there’s no unbalanced push or pull to change the motion, so the acceleration must be zero no matter the mass. Here, the block has a mass of 5 kg and experiences no net force, so its acceleration is 0 m/s^2. That means if it starts at rest it stays at rest, and if it were moving, it would continue moving at the same speed in a straight line.

If you ever wondered how the other numbers could appear, you’d need a nonzero net force: for a 5 kg mass, an acceleration of 1 m/s^2 would require 5 N of net force, 5 m/s^2 would require 25 N, and 10 m/s^2 would require 50 N.