Shelly experiences a backward jolt when the driver starts the school bus. Which of the following explains this phenomenon? A. the inertia of Shelly B. the inertia of the bus C. the normal force of the seats on Shelly D. the net force acting on Shelly in a backward direction E. a zero net force acting on Shelly

Answer: A. The inertia of Shelly

Explanation:

We know from Newton's first law that an object does not changes its state of rest or motion until an unbalanced external force exerts on it. This is also known as law of inertia. Initially Shelly and school bus are in rest state. when the driver starts the school bus and moves forward, Shelly experiences a backward jolt. This is because initially Shelly was in rest state but the bus started moving so she would feel a backward pseudo force.

A.

Newton's first law. When the bus starts, Shelly is still at rest so she resists motion. (When the bus stops, she'll jolt forward)