P9 force + momentum

• the momentum of an object is defined as the product of its mass and velocity, it is a vector quantity with the same direction as the velocity of the object
• the equation for momentum is p = mv

  p is momentum in kgms^-1

  m is mass in kg

  v is velocity in ms^-1
• momentum is always conserved in an interaction where no external forces act

  this means that total momentum before = total momentum after
• the impulse of a force is defined as the force multiplied by the time which the force acts for
• the equation for impulse is F Delta(t) = Delta(mv)​
• the impulse is equal to the change of momentum of an object
• the area under a force-time graph is the change of momentum so is the impulse of the force
• the more force an object experiences in an impact, the further it will move
• the impact changes the momentum of the object in a very short time as it is only effective when the impact force is in contact with the object
• for a given change of momentum, the force is reduced is the impact time is increased, and the force is increased if the impact time is reduced
• newton’s third law of motion: when two objects interact, they exert equal and opposite forces on each other
• the principle of conservation of momentum states for any system with no external forces acting, the total momentum before an event is equal to the total momentum after
• an elastic collision is a collision where there is no loss of kinetic energy
• an inelastic collision is a collision where there is loss of kinetic energy
• the kinetic energy lost in an inelastic collision is transferred to the surroundings
• to work out if a collision is elastic or inelastic, find the kinetic energy before and after it happened
• when two objects fly apart after being initially at rest, they move away from each other with equal and opposite amounts of momentum
• total momentum would be the momentum of both objects added together, and momentum must be conserved and was initally zero, so both objects must have zero momentum