Laws of motion (Newton) and the conservation of energy: a summary

Here is a reminder of Newton’s 3 laws of motion. Learn them and return to them often. They are fundamental to the study of braking.

1. Newton’s first law of motion:

An object at rest tends to stay at rest and an object in motion tends to stay in motion in a straight line at a constant speed.

2. Newton’s second law of motion:

F = ma
where F is force, m is mass and a is acceleration.

3. Newton’s third law of motion:

For every force, there is an equal and opposite reacting force.

Finally, keep in mind the law of conservation of energy. This law is applicable to all types of energy and can be stated as follows: The total energy at the end of any event is the same as the total energy before the event.



With all these different factors at work, can we really calculate stopping distance?

The answer is yes, although there are many variables.

If the brakes are working properly, the minimum stopping distance for a vehicle is determined by:

- the driver’s reaction time

- the coefficient of friction between the tyres and the road

The friction force of the road has to do enough work on the car to eliminate its kinetic energy. While the wheels are still turning during braking, static friction is at work. If the wheels lock up and slide over the road surface, the braking force is a kinetic friction force.




Please publish modules in offcanvas position.