Question

amy gets up from her seat on a train to move closer to the front. just as she begins to walk forward, the train stops at a station.
what is the best explanation of what happens to amy?
while amy is walking, her body is in motion. when the train stops, because shes not buckled in, amy continues to move forward due to inertia.
while amy is walking, she is in motion due to the force of repulsion. when the train stops, she is catapulted forward due to the trains stronger force of attraction.
while amy is walking, her body is in motion. when the train stops, an unbalanced force accelerates her body backward.
while amy is walking, her body is in motion, but as the train stops, it exerts a force on amy opposite to the direction she is walking, causing her to stop as well.

Explanation:

According to Newton's first law of motion (law of inertia), an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Amy was in motion (walking forward on the moving train). When the train stops, there is no seatbelt (no external force to stop her motion immediately). So, her body continues to move forward due to inertia.

• The second option is wrong because there is no such thing as "force of repulsion" and "force of attraction" in this context related to the train - Amy situation in a non - magnetic sense.
• The third option is wrong as there is no unbalanced force accelerating her backward. The train stopping affects the train's motion, not a force that would accelerate her backward.
• The fourth option is wrong because the train stopping doesn't exert a force on Amy in the opposite direction of her walking (in the sense of stopping her motion immediately without an external restraint like a seatbelt).

Answer:

While Amy is walking, her body is in motion. When the train stops, because she's not buckled in, Amy continues to move forward due to inertia.