ALL THE PHYSICS CONTENT

• Distance


  Measured in metres (m)
• Time


  Measured in seconds (s)
• Speed

  Measured in metres per second (m/s)
• Speed is defined as the distance moved per unit time
• Speed equation


  s = d/t
• Other speed equations


  1. t = d/s

  2. d = s x t
• The answer must have units of seconds when calculating time
• It's safer to use all values in metres and seconds rather than km and minutes
• Acceleration

  Defined as the change in velocity (or speed) per second
• Acceleration equation


  a = Δv/t
• Other acceleration equations


  1. t = Δv/a

  2. Δv = a x t
• Change in velocity


  Measured in metres per second (m/s)
• Acceleration


  Measured in metres per second squared (m/s^2)
• Distance-time graphs


  • Steepness indicates speed
  • Flat line indicates stationary
  • Increasing steepness indicates acceleration
• Velocity-time graphs


  • Slope is acceleration
  • Area under graph is distance travelled
• Force is a push or pull acting on an object, measured in newtons (N)
• Newton's 1st law: An object will remain at rest or in constant motion unless acted upon by an external force
• Inertia is the resistance of an object to changes in its motion
• Momentum


  How much 'motion' an object has, calculated as mass x velocity
• Newton's 2nd law


  Force = change in momentum / time
• Newton's 2nd law can be simplified to F = ma when mass is constant
• Mass


  Measure of how much matter an object has, measured in kg
• Weight


  Measure of the force of gravity on an object, measured in N
• Weight = mass x gravitational field strength (g = 10 N/kg)
• Newton's 3rd law: For every action, there is an equal and opposite reaction
• W


  Mass x 10
• Newton's 3rd law: In an interaction between 2 bodies, A and B, the force exerted by body A on body B is equal and opposite to the force exerted by body B on body A
• No force can act alone
• The action/reaction pair of forces are always on different objects, and so never 'cancel' out
• The effect of these two resultant forces is that both objects accelerate in opposite directions
• Applying Newton's laws


  1. Draw a free body diagram to show the forces acting on one object at a time

  2. Use Newton's 2nd law to calculate acceleration when forces are unbalanced

  3. Use Newton's 1st law when forces are balanced (terminal velocity)
• Terminal velocity


  The speed at which the air resistance force equals the weight force, resulting in zero acceleration
• When the parachute is opened, air-resistance increases suddenly, and so speed decreases (parachutist DOES NOT GO UP!) until the forces balance again. A new terminal velocity is reached
• Work done


  A force acting on an object causing some energy to be transferred
• Kinetic energy, KE


  The energy of a moving object
• Potential energy, PE


  The energy an object has because of its position (usually its height above ground)
• The law of conservation of energy states that energy can't be created or destroyed, only transferred from one form to another
• Friction and air-resistance tend to act on moving objects, which change some of the energy into heat & sound
• Stopping distance


  The distance a vehicle travels before it comes to a complete stop
• Thinking distance


  The distance travelled whilst reacting to a situation (before the driver applies the brakes)