momentum & impulse Flashcards
linear momentum
product of the mass and velocity of the object
p= mv (kg.m.s^-1)
(vector , in same direction as velocity vector)
newton’s second law in terms of momentum:
The net force acting on an object is equal to the rate of change of momentum.
impulse ( J )
the product of the net force and the contact time
impulse-momentum theorem
a resultant force is needed to bring about a change of momentum of an object. The longer this force acts on the object, the greater its change in velocity thus the greater the change in momentum
impulse and safety
when a vehicle is brought to a rapid rest, there is a specific charge of momentum required (Fnet = change in momentum over tine). If the time over which the momentum is increased, the force that must be applied will be less and thus less injury is caused. Airbags + crumple zones increase tine taken for passengers to be brought to rest and thus the force experienced by the passengers will be less and thus, less injury is caused.
law of conservation of linear momentum
total linear momentum of an isolated system remains constant
(total momentum of system before = total momentum of system after)
isolated system
a system that is free from the influence of a net external force that alters the momentum of the system.
external forces
forces that originates from a source other than the two objects of the system
internal forces
forces acting between the objects themselves within the system
elastic collision
A collision in which both momentum and kinetic energy are conserved
inelastic collision
a collision in which only momentum is conserved
types of collisions
collide w/ no couple
collide + couple
explosion/spring/firearm
calculate momentum
unit kg.m.s^-1
needs direction
calculate change in momentum
final - initial
calculate impulse
unit N.s
J= change in p
J on other object exerting force will be equal but opposite (N3)
