A car is moving down a straight road.Suddenly a cat jumps in front of the car.The driver slams on the breaks and the passenger goes flying forwards.Why?What law of Newton applies to this situation?

http://www.physics4kids.com/files/motion_laws.html

In this situation, the passenger goes flying forwards due to a concept known as inertia, which is one of Newton's laws of motion.

Newton's first law of motion, also known as the law of inertia, states that an object at rest tends to stay at rest, and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an external force.

When the car comes to a sudden stop, the car decelerates rapidly, while the passenger continues to move forward at the car's previous speed due to their inertia. This is because the passenger's body has a tendency to resist changes in its state of motion.

So, when the car suddenly stops, the passenger's body remains in motion due to inertia, causing them to continue moving forward until they are stopped by another force, such as the seatbelt or the dashboard. This sudden change in motion can cause the passenger to go flying forwards.

It is worth noting that wearing seatbelts can significantly reduce the risk of injury in such situations, as they provide an additional force to stop the passenger's forward motion and help prevent them from being thrown out of their seat.