How does inertia affect a person who is not wearing a seatbelt during a collision?

How does kinetic energy affect the stopping distance of a vehicle traveling at 30 mph compared to the same vehicle traveling at 60 mph?

How does kinetic energy affect the stopping distance of a small vehicle compared to a large vehicle?

Keeping in mind the kinetic energy of a moving vehicle, how can a driver best prepare to enter sharp curves in the roadway?

Using information about natural laws, explain why some car crashes produce minor injuries and others produce catastrophic injuries.

1. According to Newton's first law / law of inertia, an object that is in motion will want to stay in motion and an object at rest will want to stay at rest. From the frame of reference of the passengers in a car, we are at rest the whole time compared to the car which is moving. When a collision occurs, passengers initially at rest are suddenly put into motion towards the front windshield of the car. So, if they don't have their seatbelt on then they will fly out of the window because of the sudden change in motion due to the collision. If they had their seatbelt on, the force of the seatbelt holds the person back preventing the passenger to get too hurt.

2. The faster the vehicle is travelling the greater the kinetic energy it will have. Because the speed is squared, doubling the speed will cause the kinetic energy to increase by a factor of 4. So because of this increase in kinetic energy, the stopping distance of the faster vehicle will be much greater than the slower vehicle. Assuming that both vehicles are the same, the force of friction applied by the road on the vehicles will be the same magnitude, so it will take a longer time for the faster vehicle to come to a stop.

3. Another factor that effects the amount of kinetic energy an object will have is the mass. So the greater the mass of the object the more kinetic energy it will have, therefore resulting in a longer stopping time and a farther stopping distance.

4. When approaching a sharp curve, the driver should reduce the speed of the car to a speed below maybe 40mph about 100m away so that the vehicle doesn't have such a great kinetic energy that it will slide out onto the roadway instead of safely making a turn.

5. Some car crashes involve vehicles that are accelerating at high speeds while others involve vehicles accelerating at low speeds. For collisions involving high speed accelerations, according to Newton's second law, the greater the acceleration the more force there is. So, when two vehicles accelerating at high speeds collide, they apply a very high magnitude of force on each other, therefore resulting in catastrophic injuries. If the vehicles had a very small acceleration then there would be less force on each car, resulting in minor injuries.