A 5 kg block on a horizontal surface experiences a net horizontal force of 12 N. What is its acceleration?

• A. 2.4 m/s^2
• B. 2.0 m/s^2
• C. 4.8 m/s^2
• D. 1.2 m/s^2

Answer: (A)

Newton's second law says that acceleration equals the net force acting on an object divided by its mass. Here, the block has a net horizontal force of 12 N and a mass of 5 kg, so a = 12 N / 5 kg = 2.4 m/s^2. The acceleration points in the same direction as the net force, so along the horizontal in that direction. In other words, the block speeds up by about 2.4 m/s each second (assuming the force remains $12$ N). For context, different net forces would give different accelerations: for example, 10 N would yield 2.0 m/s^2, and 24 N would yield 4.8 m/s^2.