Chapter 8 Forces Sciences

• Contact forces


  • Friction
  • Elastic force
• Non-contact forces


  • Magnetic force
  • Gravitational force
  • Weight
• Weight


  Gravitational force exerted on an object
• Weight may change with location
• SI unit of weight

  Newton (N)
• Spring balance


  Can be used to measure weight
• Mass


  The amount of matter in an object
• Mass remains constant regardless of location
• SI unit for mass

  Kilogram (kg)
• Electronic balance, beam balance


  Can be used to measure mass
• Force

  • Can change the state of rest or motion of an object
  • Can cause a turning effect about a fixed point called a pivot
  • Can cause changes in size and/or shape of an object
  • Can cause changes in pressure of an object
• Pressure

  • Increases when a larger force is applied
  • Increases when a force is applied over a smaller area
• SI unit for pressure


  Newton per square metre or Pascal
• The Pascal is the SI unit of pressure
• Work

  Energy transferred through the application of force
• For work to be done

  • A force is applied on the object
  • The object moves
  • The object moves in the same direction as the force applied on it
• Energy


  The ability to do work
• Living things need energy for the processes that keep them alive and active
• Non-living things also need energy to work
• Energy can only change from one form to another. This is known as the law of conservation of energy
• The total amount of energy before and after the change is exactly the same. We say the total amount of energy is conserved
• Mass


  A measure of the amount of matter in an object
• Mass vs. weight


  Mass is a measure of the amount of matter in an object, while weight is a force that depends on an object's mass and the acceleration due to gravity