If a block on a frictionless horizontal surface experiences no net horizontal force, what is its acceleration?

If a block on a frictionless horizontal surface experiences no net horizontal force, what is its acceleration?

• A. a = g
• B. a = 0
• C. a = 0 m/s^2
• D. a = 9.8 m/s^2

Answer: (C)

The block has no net horizontal force, so its horizontal acceleration is zero. According to Newton’s second law, a = F/m, and with F = 0, the acceleration a = 0. This means the block’s velocity along the surface doesn’t change: if it starts at rest, it stays at rest; if it’s already moving, it keeps moving at the same speed in the same direction. On a frictionless horizontal surface gravity is balanced by the normal force, so there’s no vertical acceleration either, but the question is about horizontal motion, where the acceleration is zero. The standard way to express this is 0 m/s^2.

The block has no net horizontal force, so its horizontal acceleration is zero. According to Newton’s second law, a = F/m, and with F = 0, the acceleration a = 0. This means the block’s velocity along the surface doesn’t change: if it starts at rest, it stays at rest; if it’s already moving, it keeps moving at the same speed in the same direction. On a frictionless horizontal surface gravity is balanced by the normal force, so there’s no vertical acceleration either, but the question is about horizontal motion, where the acceleration is zero. The standard way to express this is 0 m/s^2.