In a non-inertial frame accelerating to the right with acceleration a, what is the fictitious force that appears on a mass m?

In a non-inertial frame accelerating to the right with acceleration a, what is the fictitious force that appears on a mass m?

• A. F_fictitious = m a to the left
• B. F_fictitious = m a to the right
• C. F_fictitious = - m g
• D. F_fictitious = 0

Answer: (A)

In a frame that accelerates to the right, you introduce a fictitious force that acts opposite to the frame’s acceleration. Its magnitude is m a. So the mass experiences a fictitious force of m a to the left. This is what keeps Newton’s laws working in a non‑inertial frame: the fictitious force compensates for the frame’s acceleration. Gravity is a real force downward, and the fictitious force is not zero in a non-inertial frame, nor is it to the right.

In a frame that accelerates to the right, you introduce a fictitious force that acts opposite to the frame’s acceleration. Its magnitude is m a. So the mass experiences a fictitious force of m a to the left. This is what keeps Newton’s laws working in a non‑inertial frame: the fictitious force compensates for the frame’s acceleration.

Gravity is a real force downward, and the fictitious force is not zero in a non-inertial frame, nor is it to the right.