E-Lecture - Important Points
- Linear momentum is a vector quantity and it is defined as the product of mass and velocity.
- Newton’s second law of motion can be restated as net force is equal to the time rate of change of momentum.
- Impulse is defined as the product of the average force applied and the duration for which the force is acted. It is equal to the change of momentum.
- The area under net force versus time graph provides the impulse or the change of momentum.
- A collision is an interaction between two objects in which a force acts on each object for a period of time.
- Kinetic energy is the energy possessed by a body due to its motion. Ek =
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- In an elastic collision, both momentum and kinetic energy are conserved. In an inelastic collision, momentum is conserved but kinetic energy is not. In a perfectly inelastic collision, momentum is conserved, kinetic energy is not, and the two objects stick together after the collision, so their final velocities are the same.
- For any system, the forces that the particles of the system exert on each other are called internal forces. Forces exerted on any part of the system by some object outside it are called external forces.
- For an isolated system in which there is interaction among particles, the total momentum of the system is constant, even though the individual momenta of the particles that make up the system can change.
- The momentum of an isolated system is conserved, but not necessarily the momentum of one particle within that system.
- The angular momentum of a rotating object is given by L = r x P
- Angular momentum can also be expressed as L = Iω
- Angular momentum is related to torque as
- If the net external torque acting on a system is zero, the total angular momentum of the system is constant and is said to be conserved, Li = Lf
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