Physics

• Distance


  Can be measured in mm, cm, m and km
• Time


  Measured in ms, s, mins and hours
• Speed


  Calculated as distance/time
• Vector


  Has magnitude and direction
• Scalar


  Has just magnitude
• Speed is scalar and velocity is vector as it gives speed in a given direction
• Distance-Time Graphs


  • Gradient shows velocity
  • Steeper gradient = faster speed
  • Negative gradient = object returning to starting point
  • Horizontal line = object stationary
• Velocity-Time Graphs


  • Gradient shows acceleration
  • Steeper gradient = greater acceleration
  • Negative gradient = object decelerating
  • Horizontal line = constant speed
• Average speed


  Calculated as total distance/total time
• Electrostatic interaction


  Force of attraction or repulsion between charged particles
• Gravitational attraction


  Force between particles with mass
• Contact forces


  Forces experienced in the opposite direction to contact, such as friction
• Free body force diagrams

  • Reaction force acts normal to line of contact
  • Friction acts opposite to movement
  • Weight acts vertically downwards
• Scale drawings


  • Length of arrows represents force size
  • Arrows in opposite directions of equal length = forces cancel out
• Newton's First Law


  Object has constant velocity unless acted on by a resultant force
• Newton's Second Law


  Acceleration or deceleration depends on direction and magnitude of resultant force
• Inertia


  Measure of how difficult it is to change an object's velocity based on its mass
• Momentum


  Depends on mass and velocity
• In an elastic collision, momentum and kinetic energy is conserved
• Newton's Third Law


  Every action force has an equal and opposite reaction force
• Work done


  Energy transferred from object doing work to another form, calculated as force x distance
• Elastic deformation


  Object returns to original shape when load removed
• Plastic deformation


  Object does not return to original shape when load removed
• Hooke's Law


  Force applied to spring = spring constant x extension
• Weight


  Force exerted on mass by gravitational field, calculated as mass x gravitational field strength
• Gravitational potential energy


  Depends on mass, gravitational field strength and height
• Moment of a force

  Force x perpendicular distance
• Gears


  Can change speed, force or direction by rotation
• Pressure


  Force per unit area, constant in fluids
• Hydraulic brakes


  Force applied in narrow cylinder is multiplied in wider cylinders due to constant pressure in fluids