When a bus that is moving forward on a straight road suddenly accelerates
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
When a bus that is moving forward on a straight road suddenly accelerates, the passengers appear to lean backward. What is the correct explanation for this observation?
(a) The passengers push the bus floor forward, and by Newton’s third law the floor pushes them backward.
(b) In the accelerating bus frame a backward pseudo-force acts on the passengers, so they lean backward.
(c) Because the bus accelerates, the passengers’ weight effectively tilts backward, so a component of gravity pulls them toward the rear of the bus.
(d) The passengers’ feet move forward with the bus, but their upper bodies lag because they are barely in contact with the floor, causing them to tip backward.