Grade 12 Physics Concepts: Momentum
The formula for momentum is written as p=mΔv, where p=momentum, m=mass and Δv=change in velocity. Both velocty and momentum are vector quantities. Momentum describes the motion of an object in terms of its mass and velocity. Since momentum is a product of these 2 variables, increasing/decreasing either the mass or velocity will increase/decrease the momentum an object experiences. In the case of a car crash, a car will have less momentum if it has a smaller mass and is travelling at a low speed. The inverse is also applicable.
Figures 1 and 2: (1) The given variables in the momentum equation. (2) The relationship between mass and momentum in graph 1 and velocity and momentum in graph 2 illustrates the directly proportional relationship between momentum, mass and velocity.
A greater momentum means that an object is harder to stop. In order to stop an object with momentum, an unbalanced force must act on the object in the opposite direction. A greater momentum is therefore not desired when trying to avoid a fatal car crash, because if the momentum becomes too large the brakes will not be able to apply a large enough opposing force.
Figure 3: Shows the momentum of a system as a whole in the event of a car crash involving to objects of different masses moving at the same velocity in the same direction. The momentum of one car is added is added to that of the other (p of car 2 increases) while it's own momentum decreases. The momentym of the system is still constant. This is due to the law of conservation of energy, which states that the total amount of energy remains constant in an isolated system. The object with the greater momentum in this case, mass 2 (which had a greater mass), increased it's momentum, showing that in the event of a car crash an even greater opposing force would have to be applied.
