P2a

P2a

1. Forces

   • Gravity
     • Attraction between all masses
       • Causes acceleration of 10m/s
     • Gives weight
       • Newtons
     • Mass in kg
   • Resultant forces
     • Change in velocity
   • Acceleration
     • Caused by a resultant force
     • A=F/M
   • Equal and opposite force
     • When two objects interact
   • Friction
     • Increases with speed
     • Terminal velocity
       • When objects first fall, gravity is stronger than friction
         • As speed increases the friction/air resistance does until they are equal
           • No more acceleration
       • Decreased by increase in air resistance i.e. a parachute

2. Energy

   • When a force moves an objecta distance Energy is transferred and work is done.
   • Kinetic
     • 1/2*m*v^2=f*d
       • In braking
     • Elastic
       • Energy store when work done changes its shape.
       • Directly proportional between force and extension
         • Until stretched beyond limit of proprtionality when it no longer returns to its original shape
   • Power
     • Rate of work or energy transfer
     • Watts or J/s
   • Momentum
     • mass*velocity=momentum(kg m/s)
     • Momentum before=after
     • Forces cause momentum change
       • Longer the change in momentum the less the force
   • Car safety
     • Regenerative brake system
       • Kinetic energy in braking often wasted as heat.
       • These brakes put the motor in reverse and use it as a generator to store the energy in the battery
     • Increase impact time so decrease forces
     • Direct kinetic energy away from passengers

3. Electricity

   • Static
     • Two insulating materials
     • Electron transfer
   • Current
     • Flow of charge-amps
   • P.D.
     • Driving force of current or work done per unit of charge.
   • Resistance
     • Slows flow down-ohms
     • Filimant lamp
       • Resistance increases with voltage
         • Converted into heat causes ions to vibrate, current can't flow as easily-resistance
   • Charge
     • Current over time, coulombs
   • Circuits
     • Parralel
       • PD the same
       • Current split
     • Series
       • PD split
       • Current same