Momentum is the measure of an object’s motion and is calculated by multiplying the object’s mass by its velocity. Because momentum is calculated using velocity, it is a vector. That is, it has both direction and magnitude. This means that when you describe the momentum of a mass, you must provide its direction.

Momentum = Mass (Kg) X Velocity (m/s)

Momentum is directly related to the velocity of the object and its mass (often called weight). Therefore a larger object moving at the same velocity as a smaller object will have greater momentum. Momentum relates to force because force is the rate at which momentum changes with relation to time. When we are thinking about the size of an object’s momentum, we should also think about the amount of force it took to provide the object its motion, and how much force would be required in order to stop the object from moving. So the heavier object (with a larger mass) moving at the same velocity as a lighter object will require more force to stop its velocity, and took more force to get to its current velocity.

For sports performance, the all objects have mass, and therefore when in motion have momentum. Momentum is particularly important for contact sports such as rugby league. Here the forward, who is often heavier, builds up his momentum as he makes his run. This momentum requires a large force from the opposition in order to stop the motion. If the forward runs into a lighter player, the lighter player will struggle to stop the motion of the heavier forward because the forward will generally have larger momentum, even if they are moving at the same velocity in opposite directions.

Momentum also related to acceleration. In order to accelerate, the force acts upon an object. The heavier the object the larger the force that is required to move it, and the motion will be slower than a lighter object that receives or produces the same force. So the lighter full-back can move faster and accelerate more quickly than the heavier forward because the forward requires more force to reach the same velocity.

Another example can be seen in the 400m sprint. Throughout the sprint, the athlete needs to accelerate, at the beginning by increasing their speed, but as they turn corners, they need to change direction, which is also acceleration. In order to change direction, the athlete must create a force that causes them to move. This is because the athlete already has momentum in a particular direction, and needs to have another force act upon themselves (produced by their own muscles and the ground) in order to change their momentum from one direction to another. So here, the change in momentum, may not mean a change in speed, but a change in direction (a change in velocity)