An anteriorly directed GRF does what to the center of mass?

An anteriorly directed GRF does what to the center of mass?

• A. Slows it down
• B. Moves it backward
• C. Accelerates it forward
• D. Stops vertical movement only

Answer: (C)

The main idea is that the center of mass accelerates in the direction of the net external force acting on the body. A ground reaction force directed anteriorly is a forward external push on the body. By F = m a, that forward component causes forward acceleration of the center of mass. In other words, the forward GRF contributes propulsion, speeding the body up in the forward direction. The vertical component, not the anterior component, would govern vertical motion, so focusing on the forward direction, it accelerates the center of mass forward.

The main idea is that the center of mass accelerates in the direction of the net external force acting on the body. A ground reaction force directed anteriorly is a forward external push on the body. By F = m a, that forward component causes forward acceleration of the center of mass. In other words, the forward GRF contributes propulsion, speeding the body up in the forward direction. The vertical component, not the anterior component, would govern vertical motion, so focusing on the forward direction, it accelerates the center of mass forward.