MOMENTUM, IMPULSE & COLLISIONS
MOMENTUM AND ITS RELATION TO FORCE
Momentum, p = mv
Net force is equal to rate of change of momentum; F= dp / dt
CONSERVATION OF MOMENTUM
Law of conservation of linear momentum
Total momentum of an isolated system is conserved.
Total initial momentum = total final momentum m1u1 + m2u2 = m1v1 + m2v2
COLLISIONS & IMPULSE
Impulse is equal to the change of momentum
J = Ft = p final - p initial
CONSERVATION OF ENERGY & MOMENTUM IN COLLISIONS
Inelastic collision
Elastic collision
Momentum is conserved : m1u1 + m2u2 = (m1 + m2)v
Momentum is conserved : m1u1 + m2u2 = m1v1 + m2v2
Kinetic energy is not conserved- lost to thermal or potential energy
Kinetic energy is conserved : 1/2m1u1 + 1/2m2u2 +1/2m1v1 + 1/2m2v2
CENTER OF MASS (CM)
Type of collisions : explosion, inelastic, elastic
a mass-weighted average position of the particles.
Center of mass lies closer to more mass particle for two particles
same as center of gravity as long as force of gravity does not vary on an object
SYSTEM OF VARIABLE MASS;ROCKET PROPULSION
Sum of forces equal to total mass times acce;leration of CM
where v is the velocity of ejected mass with respect to the rocket