You have seen that travelling on Alberta's roads can be deadly. In this activity, you will use some of your understanding of momentum, velocity, and motion to see how accidents happen.

You have already looked at some of the scientific principles that allow you to predict the movement of vehicles in a collision. For example, you know that momentum is conserved. This knowledge allows you to calculate the changes to momentum that occur in the event of a collision.

Consider these three common scenarios for a collision between two vehicles:

• Imagine one vehicle rear-ending another vehicle. These vehicles are approximately the same size. In this example, you know that the momentum of each vehicle will be conserved, so they will continue in the same direction until the friction of the drivers applying the brakes stops the vehicles.

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• Imagine an accident where two similar cars are in a head-on collision. In this example, the momentum of the two cars will be conserved, but because they are travelling in different directions, the cars will stop.

• Now imagine an accident involving two vehicles of different sizes, such as a moving truck and a small car. They are in a head-on collision. In this example, momentum will be conserved, but the greater mass of the larger vehicle means it has more momentum, so it will likely move the smaller car backwards.

Because you know that momentum is conserved, you can make choices if you are faced with a potential collision.

You also know that mass and velocity affect momentum. Since your momentum will be greater when you are travelling at high speeds, you know that it will be safer to travel according to the speed limit or even below the speed limit if the road conditions are not ideal. As well, you know that a larger vehicle has greater momentum than a smaller vehicle travelling at the same velocity. As a result, you should be aware of the size of the vehicles near you on the road.

Another important factor you know is the role that impulse plays in changing momentum. You remember that impulse describes the amount of force and the length of time the force is applied to change momentum. You know that having to apply a great deal of force in a short time creates a large change in momentum, so you know that leaving space between vehicles when travelling gives you time to brake and avoid injuring yourself or others with a sudden, severe impulse.