Momentum (p) is the mass of the object multiplied by the velocity of the same object. It is also the objects tendency to stay in motion. For an object's momentum to change, either velocity of the object or the mass has to change. This change in momentum is called Impulse (J) which is a force over a period of time. Therefore, impulse is the area under a force vs. time graph.
Momentum a and Impulse are very closely related to Newtons second law as their relationship comes from that law.
J=∆p
F•t=m•∆v
F=m• (∆v/t)
F=m•a
F•t=m•∆v
F=m• (∆v/t)
F=m•a
That was the mathematical relationship between Momentum and Impulse
This concept of how momentum and impulse are related is helpful in understanding collisions. There are four different types of collisions-
- Completely Elastic Collisions- No kinetic energy or momentum is lost, the objects just bounce off of each other and maintain the same velocity in an opposite direction. A good example of this would be two carts that are going at each other on a frictionless surface and having magnets on either cart repel them from each other.
- Completely Inelastic Collisions- There is a loss of kinetic energy but not a loss in momentum. This is because in this situation the objects stick together which slows them down but the increase of mass makes the momentum maintain equal.
- Inelastic Collisions- In the middle of Completely Inelastic and elastic collisions so some kinetic energy is lost but all momentum is conserved.
- Explosions: This is when kinetic energy is gained but no momentum is lost. This is because objects are usually stopped and then a force causes them to explode outwards. This causes a gain in kinetic energy but the total momentum of the system stays the same.
The only way to change the momentum of a system is through an impulse. Therefore, in an isolated situation, where there is no impulse, momentum is always conserved.
A change in momentum can be represented by a bar chart that demonstrates the initial momentum, impulse and final momentum. These charts are called LIL charts.
By Jack Dolan
In this example two cars were moving at each other and then bounced off of each other. You can see that there was not a loss in momentum in the system since the bars still add up to 0. If there was a change in momentum then there would have to be a bar in the middle showing the impulse of the system in either a positive or negative way.
Widget is loading comments...