P5

• Scalar quantities

  magnitude only
• Vector quantity

  Magnitude and direction
• Examples of contact forces

  • friction
  • air resistance
  • tension
• Examples of non-contact forces

  • gravitational
  • electrostatic
  • magnetic
• Work done

  when a force causes and object to move
• Moment

  The turning effect of a force
• Upthrust


  An object experiences a greater pressure on the bottom surface than on the top surface
• The atmosphere gets less dense...

  with increasing altitude
• Distance is a ..... quantity

  scalar
• Displacement is a ..... quantity

  vector
• speed is a .... quantity

  scalar
• walking speed

  1.5 m/s
• running speed

  3 m/s
• cycling speed

  6 m/s
• speed of sound in air

  330 m/s
• velocity is a .... quantity

  vector
• How to calculate distance from a velocity-time graph?

  Area under
• Newtons 1st law

  An object remains stationary or moving at a constant speed unless a resultant force acts upon it.
• Newton's 2nd law

  Speed or acceleration of an object is directly proportional to the resultant force and inversely proportional to the mass
• Newton's 3rd law

  When 2 objects interact they apply forces that are equal in magnitude and opposite in direction.
• The greater the speed...

  The greater the breaking distance
• Reaction time of a person

  0.2-0.9 seconds
• Affects reaction time...

  • Alcohol
  • tiredness
  • drugs
• Conservation of momentum

  In a closed system the total momentum before an event is equal to the total momentum after the event.
• Safety features...

  decreases rate of change of momentum