when a car suddenly stops at a red light a book lying on the car seat slides forward why does the book continue to move forward?

Inertia.

the books inertia causes it to continue moving

Inertia

The book continues to move forward due to inertia. Inertia is a fundamental property of matter that describes an object's resistance to changes in motion. When the car suddenly stops at a red light, the rest of the car (including the car seat) decelerates, but the book tends to maintain its forward motion due to its inertia. Since there is no force acting on the book to stop it immediately, it slides forward until an external force (such as friction or contact with another surface) opposes its motion and brings it to a stop.

To understand why the book continues to move forward, let's break it down step by step:

1. The car and everything inside it, including the book and the car seat, are in motion as it moves along the road.

2. The car applies brakes to come to a stop at a red light. This action reduces the car's speed and velocity.

3. However, the book on the car seat tends to maintain its forward motion due to inertia. According to Newton's first law of motion, an object in motion will stay in motion unless acted upon by an external force. In this case, the book wants to keep moving forward as it was initially.

4. Since there is no force acting on the book to stop it immediately, it continues to slide forward on the car seat.

5. Eventually, the book will encounter friction between its surface and the car seat, which opposes its forward motion and causes it to slow down and come to a stop.

In summary, the book continues to move forward due to its inertia, following Newton's first law of motion, until an external force (such as friction) brings it to a stop.