Application: A Car Wreck

Context

This section will apply some basic math to a real life situation. The general area of investigation is linear motion. We will specifically look at horizontal motion and acceleration due to friction. This page has a general overview of linear motion.

Why do we keep going forward after slamming on the brakes? The answer to this question may seem self-evident. It is a good example of a question that seems easy on first glance, but has an answer that is so fundamental that it is difficult to answer. After some thought you might think that objects don't keep going. The car stops when you put on the brakes. Or even when you just take your foot off of the gas. A chair being pushed across the floor stops after traveling only a short distance. Billiard balls eventually stop.

Maybe these situations are too complicated. One strategy that is often used in science is to simplify as far as possible. What if we took an object (a chair) into outer space, where there are no other objects, and let it go. What would it do? This question was debated for thousands of years before an acceptable answer was found. Aristotle (384-322 BC) got it half right. It was Galileo Galilei (1564-1642) who studied motion carefully enough to be able to correctly answer the question. He came up with the notion of inertia and developed the conceptual framework for Newton (1642-1727) to build on. Newton was one of the greatest scientists of all time. He established the laws of motion that are still used today, invented the mathematical basis for calculus, and showed that all large bodies obey the same physical laws. He knew that the chair, if placed at rest, would remain at rest, or if placed in motion, it would continue in a straight line motion.

Newton's laws are so fundamental to understanding many every day observations that we will have to investigate them in more detail before moving on.

What is linear motion?

Simply put, linear motion is motion along a line. It is straight line motion.

Explanation

Scientists have observed that perpendicular motions are independent of each other. The horizontal motion is independent of the vertical motion since the horizontal and vertical are perpendicular (at 90^o) to each other. This is significant because it allows all problems to be broken down into straight-line, or linear, components that can be treated independently. That makes these problems much easier to deal with. We can apply Newton's laws independently to each direction and then combine the directions to get a final result. In this course we will only consider motion in one direction (horizontally).

This section will help you:

• Understand motion without acceleration.
• Describe how friction causes a change in motion horizontally.

Model

The model for this section is broken up into two parts. The menu on the left gives you access to each of these parts.