# Physics Topic 4

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• Transport on the Track
• Momentum
• P = MV
• Units =kgms-1 Vector quantity
• Monentum  of an object is a measure of the accelerating force, applied over a period of time, that is needed to bring an object from rest to the speed at which it is moving
• It could also be the force required over a period of time to bring the moving object to rest.
• Newton's Second Law
• F= MA
• Formula only holds true if mass remains contestant
• The rate of the change in momentum of a body is directly proportional to the resultant force applied to the body, and is in the same direction as the force
• F =  ?p/?t
• The product of a force applied  over a certain time is known as an impulse ?p  = ?t x F
• Conservation of momentum
• Initial momentum = final momentum
• when no external forces act (in a closed  system)
• Explosions
• If a staintory object eplosed the total momentum of all its parts will be zero
• Because the initial momenum was zero!!
• Newtons third Law
• For every force there is an equal and opposite force
• In terms of momentum this means that for any forcing changing momentum in one direction must be encounter by an equal and opposite force to ensure over al momentum is conserved
• Collisions
• Elastic collison= kinetic energy is conserved
• Newtons cradle - a collision causedby non contact forces such as alpha particles being    scattered by a nucleuses perfectly elastic
• Inelastic collisions are when keneticenergy si not conserved by transferred to other energy forms e.q. heat
• Ek = p2/2m
• 1 eV = 1.6 X10-19
• Circular motion
• w = 2?f
• f-1/T
• Centripetal force = the force that causes acceleration towards the centre of the circle
• Fprce will be larger if the object has a large mass, the radius is small or is the velocity is large