P8

• What is a scalar quantity?


  A scalar quantity has magnitude only.
• What is a vector quantity?


  A vector quantity has both direction and magnitude.
• How can vectors be represented visually?


  Vectors can be denoted with an arrow to represent the size and direction.
• What are some examples of scalar quantities?


  • Speed
  • Distance
  • Mass
  • Temperature
  • Time
• What are some examples of vector quantities?


  • Velocity
  • Displacement
  • Force
  • Momentum
  • Acceleration
• What does Newton's 1st Law state?


  An object will remain at rest, or in constant motion, unless acted on by an external net force.
• What does Newton's 3rd Law state?


  When two objects interact, the forces they exert on each other are equal and opposite.
• What is a resultant force?


  A resultant force is a single force that summarizes many forces acting on an object.
• What happens if an object has a resultant force that is not zero?


  It must be undergoing a change in motion (an acceleration or a deceleration).
• What does it mean if an object has a resultant force of zero?


  It must be stationary or in constant motion (Newton's 1st Law).
• What are examples of contact forces?


  1. Friction
  2. Tension
  3. Air-resistance
  4. Reaction
  5. Upthrust
• What are example of non-contact forces?


  1. Weight
  2. Magnetic
  3. Electrostatic
• Centre of mass 


  The point where an objects mass can be thought of as being concentrated
• Where is the centre of mass of a symmetrical object?


  Where all the lines of symmetry overlap
• How do you find the centre of mass of a non-symmetrical object?


  1. Object should be suspended from same point as a plumb line
  2. Line should be drawn directly from point of suspension to ground following plumb line
  3. Repeat with object suspended from different points
  4. Where the lines overlap is the centre of mass
• Why does the suspension method work?

  When objects are suspended, they always come to rest with their centre of mass directly under the point of suspension
• Moment 


  The turning effect produced by a force
• Principle of moments


  For a body in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments