Linear motion simply means motion in a straight line (as opposed to circular motion or rotation). In order to talk about linear motion scientifically, we need to be familiar with mass, distance, displacement, speed, velocity, and acceleration. Here we explain Newton's laws of motion, mass, inertia, momentum, speed, velocity, distance, displacement and graphs of motion.
Sir Isaac Newton stated three laws which explain the relationship between force and movement. Having an understanding of Newton's laws which you can apply to sporting situations gives you a deeper understanding of sports technique.
Inertia is the reluctance of a body to change whether it is moving or not and is related to its mass. Once a body is moving the momentum of the body is a product of its mass multiplied by its velocity.
Graphs are a good way of showing motion. The two types of graphs which are of most interest are distance/time graphs and speed/time (or velocity/time) graphs. Graphs are particularly useful when things are moving too fast for the naked eye and brain to understand what is happening, which is often the case in sport.
Acceleration is the rate at which a body changes its velocity and is also a vector quantity which needs a direction as well. It is measured in m/s/s or metres per second per second (metres per second squared - m/s2).