physics

• Ruler


  Can measure small distances of a few centimetres (cm) to the nearest millimetre (mm)
• Tape measure


  Used to measure larger distances of a few metres
• Trundle wheel


  Used to measure even larger distances
• Measuring cylinder


  Used to measure the volume of liquids and irregular shaped solids
• Measuring the diameter of ball-bearings

  1. Measure the total length of 4 ball-bearings

  2. Divide the total length by the number of ball-bearings
• Stopwatch/stop-clock


  Used to measure time intervals
• Human reaction time can have a significant impact on very short time measurements (less than a second)
• Calculating time taken for a runner to complete a lap

  1. Identify the start time

  2. Identify the finish time

  3. Convert the finish time to seconds

  4. Calculate the time taken by subtracting the start time from the finish time
• Information given in a question that is not needed for the calculation is a common method to make the question seem more difficult
• Multiple readings


  Taking a reading of a large number of values and then dividing by the number to get an accurate value for a small figure
• Scalar


  A quantity that has only a magnitude
• Vector


  A quantity that has both magnitude and direction
• Scalars


  • Mass
  • Distance
• Vectors


  • Velocity
  • Displacement
• Distance is a scalar quantity since it only contains a magnitude, not a direction
• Displacement is a vector quantity since it describes both the magnitude and direction of the distance
• Examples of scalars and vectors


  • Scalars: mass, distance, time, speed, energy, temperature
  • Vectors: velocity, displacement, force, acceleration, momentum
• Determining if a quantity is scalar or vector


  Identify if the quantity has magnitude only (scalar) or magnitude and direction (vector)
• Vectors


  Represented by an arrow, the arrowhead indicates the direction, the length represents the magnitude
• Component vectors


  Drawn with a dotted line and a subscript indicating horizontal or vertical
• Calculating vectors graphically


  1. Choose a scale

  2. Draw the vectors at right angles

  3. Complete the rectangle

  4. Draw the resultant vector diagonally from the origin

  5. Measure the length and angle of the resultant vector
• Combining vectors by calculation

  1. Draw a diagram with the resultant, component and sides labelled

  2. Use Pythagoras' Theorem to find the resultant vector

  3. Use trigonometry to find the angle
• If the question specifically asks you to use the calculation or graphical method, you must solve the problem as asked
• The graphical method sometimes feels easier than calculating, but once you are confident with trigonometry and Pythagoras you will find calculating quicker and more accurate
• Pythagoras' Theorem


  Makes calculating vectors at right angles much simpler
• Trigonometry


  Essential in vector calculations, the mnemonic 'soh-cah-toa' is used to remember how to apply sines and cosines
• Speed


  The distance an object travels per unit time
• Speed


  • It is a scalar quantity (only contains a magnitude, no direction)
  • For objects moving at constant speed, use the equation: speed = distance / time
• Speed


  • A hiker's average speed of 2.0 m/s
  • A bumble bee's average speed of up to 4.5 m/s
• Average speed


  The total distance travelled divided by the total time taken
• The formula for average speed can be rearranged using a formula triangle
• Velocity


  The speed of an object in a particular direction (a vector quantity)
• Velocity can have a negative value, e.g. a ball thrown upwards at 3 m/s comes down at -5 m/s
• The equation for velocity is: velocity = displacement / time
• Acceleration


  The rate of change of velocity
• Change in velocity


  Final velocity - initial velocity
• An object that speeds up is accelerating
• An object that slows down is decelerating
• Positive acceleration


  When an object is speeding up
• Negative acceleration


  When an object is slowing down (also called deceleration)