Physics unit 1

• Dimension


  The relation between a physical quantity and the base quantities
• Dimensions of base quantities

  • Mass [M]
  • Length [L]
  • Time [T]
  • Temperature [θ]
  • Electric current [A]
• Derived physical quantity


  A quantity that is derived from a combination of base quantities
• Examples of derived physical quantities and their dimensions

  • Area [L]2
  • Volume [L]3
  • Density [M L-3]
  • Acceleration [L T-2]
  • Power [M L2 T-3]
• Dimensions can be used to deduce the dimensions of a derived quantity
• Dimensions can be used to check the homogeneity of an equation
• In any scientific equation, the units on the left-hand side must equal the units on the right-hand side
• Scalar quantity


  Quantity with magnitude only
• Vector quantity


  Quantity with magnitude and direction
• Examples of scalar quantities

  • Mass
  • Length
  • Work
  • Speed
  • Distance
  • Energy
  • Power
• Examples of vector quantities

  • Weight
  • Momentum
  • Velocity
  • Acceleration
  • Displacement
• Representing a vector


  A straight line with an arrow at one end, length represents magnitude, direction of arrow represents direction
• Adding scalars


  Add numerically
• Adding vectors


  Draw vector a, then draw vector b starting from the end of a, the resultant vector a+b is drawn from the start of a to the end of b
• Subtracting vectors


  Draw vector a, then draw -b (same length as b but opposite direction) starting from the end of a, the resultant vector a-b is drawn from the start of a to the end of -b
• Vectors acting in the same direction

  Resultant force is the sum of the magnitudes
• Vectors acting in opposite directions


  Resultant force is the difference of the magnitudes, in the direction of the larger force
• Vectors acting at an angle


  Resultant force can be calculated using the cosine rule
• Resolving a vector


  Replace a vector with two vectors acting at right angles (x-component and y-component)
• Metre rule


  Used to measure lengths of objects like desks and pendulums
• Vernier calliper


  Used to measure small dimensions like diameter of test tubes
• Micrometer screw gauge


  Used to measure very small lengths like diameter of wires
• Beam balance


  Used to measure mass of objects

  
• Spring balance


  Used to measure weight (force) of objects
• Protractor


  Used to directly measure angles
• Spectrometer


  Used to precisely measure angles in optics experiments
• Thermometer


  Used to measure temperature
• Volume


  Amount of space taken up by an object
• Measuring volume of regular objects


  Calculate using formulas (cuboid, sphere, cylinder)
• Measuring volume of irregular objects

  Use displacement method - measure volume of water displaced
• Meter


  Instrument used to measure length
• Spectrometer


  Instrument used to measure angles in optical experiments
• Thermometer


  Instrument used to measure temperature
• Kelvin (K)


  SI unit of temperature
• Degrees Celsius (°C)


  Unit used to measure temperature
• Volume


  The amount of space taken up by an object
• Measuring volume of a regular object

  1. Calculate using formula

  2. Volume of cuboid: V = l × b × h

  3. Volume of sphere: V = 4/3πr^3

  4. Volume of cylinder: V = πr^2h
• Measuring volume of an irregularly shaped object

  1. Use displacement method

  2. Place object in water in measuring cylinder

  3. Record initial and final volume

  4. Difference is volume of object
• Standard instruments used to measure length

  • Metre rule
  • Vernier caliper
  • Micrometer screw gauge
• Mass


  Measured using beam balance or electronic balance