Question

Selvi placed her purse on the passenger seat of her car when she drove to her office. But, by the time she reached her office, her purse had fallen on to the floor in front of the passenger seat. Explain why this happened.

Answer 1

Hint: Newton’ s first law of motion introduces the concept of inertia. Inertia is a property of a body which allows it to continue its state of rest or uniform motion in a straight line unless it gets acquainted with an external force. Here, Selvi’s car is a case of uniform motion in a straight line until it comes to rest.

Complete step by step answer:
Step 1: Define Newton’ s first law of motion.
Newton’ s first law of motion states that every body continues its state of rest or uniform motion in a straight line unless compelled by some external force to act otherwise.
Step 2: Describe what happened when Selvi stopped the car based on the first law of motion.
When Selvi started her journey to work her purse was placed on the seat. So, her car and everything inside it including her purse was in a state of motion with respect to an observer outside the car. As soon as she reached her office, she stopped the car by hitting the brakes. But due to inertia of motion her purse continued its state of motion until it was stopped by the body of the car. As a result, her purse fell forwards onto the floor.

Additional Information: An instance where the inertia of rest comes in to play is when we get thrown backwards with a jerk when the driver starts the bus suddenly. This happens because we are in a state of rest and this state ceases when the driver starts the bus suddenly. Also when the driver applies brakes we feel a sudden jerk in the forward direction due to inertia of motion, as we were in a state of motion and suddenly brought to rest.

Note: Inertia of rest allows a body to continue its state of rest while inertia of motion allows the body to continue its state of motion.