Physical Quantities and Measurement Techniques

PHYSICAL QUANTITIES AND SYLLABUS OVERVIEW (PAGE 1)

Core Measurement Skills

  • Use rulers and measuring cylinders for length and volume measurements.
  • Use clocks and digital timers for time intervals.
  • Calculate average values for small distances and short time intervals (e.g., period of oscillation of a pendulum) using multiples.

Scalar and Vector Quantities (Supplement)

  • Scalars (Magnitude only): distance, speed, time, mass, energy, and temperature.
  • Vectors (Magnitude and direction): force, weight, velocity, acceleration, momentum, electric field strength, and gravitational field strength.
  • Vector Addition: Graphically or mathematically determine the resultant of two vectors at right angles (limited to forces and velocities).

MEASUREMENT OF LENGTH AND VOLUME (PAGES 2-8)

Core Vocabulary

  • Ruler, Measuring Cylinder, Length, Volume, Digital Timer, Oscillation, Period, Average.

Instruments for Length

  • Rulers: Small distances (nearest mmmm).
  • Tape Measure: Tens of centimetres (cmcm).
  • Trundle Wheel: Tens of metres (mm).

Measuring Volume

  • Measuring Cylinders: Used for liquid volume.
  • Displacement Method: Used for irregular shapes by measuring the change in liquid volume.

Calculating Averages: Ball-Bearings Example

  • To find the diameter of a single small object, measure a group and divide: diameter=total lengthnumber of ball bearings\text{diameter} = \frac{\text{total length}}{\text{number of ball bearings}}
  • Example: 8 cm4 bearings=2 cm\frac{8\,cm}{4\text{ bearings}} = 2\,cm

MEASURING TIME AND REACTION (PAGES 9-11)

Time Measurement

  • Primary instruments: Stop-clocks and stopwatches.
  • Human Reaction Time: Typically 0.25 s0.25\,s for an alert person; significant for very short interval measurements.

Calculating Time Intervals

  • Calculation: total time=finish time−start time\text{total time} = \text{finish time} - \text{start time}
  • Example Runner Lap:    - Start: 55.10 s55.10\,s    - Finish: 105.10 s105.10\,s (1 min 45.10 s1\text{ min } 45.10\,s)    - Total: 50 s50\,s

MULTIPLE READINGS AND SI UNITS (PAGES 12-17)

Accuracy through Multiples

  • Multiple readings reduce measurement error impact.
  • Thickness of one sheet: thickness of stacknumber of sheets\frac{\text{thickness of stack}}{\text{number of sheets}}
  • Example: 23 mm100=0.23 mm\frac{23\,mm}{100} = 0.23\,mm

The SI Base Units

  • Mass: Kilogram (kgkg)
  • Length: Metre (mm)
  • Time: Second ($s$)
  • Other Units: Ampere (AA) for current, Kelvin (KK) for temperature.

Scale and Notation

  • Time: Millisecond (10−3 s10^{-3}\,s), microsecond (10−6 s10^{-6}\,s), nanosecond (10−9 s10^{-9}\,s).
  • Length: Kilometre (103 m10^{3}\,m), centimetre (10−2 m10^{-2}\,m), millimetre (10−3 m10^{-3}\,m), micrometre (10−6 m10^{-6}\,m), nanometre (10−9 m10^{-9}\,m).
  • Mass: Tonne (103 kg10^{3}\,kg), gram (10−3 kg10^{-3}\,kg), milligram (10−6 kg10^{-6}\,kg).

Scientific Definitions

  • Metre: Distance light travels in a vacuum in 1299 792 458\frac{1}{299\,792\,458} of a second.
  • Second: Frequency of an oscillation in the nucleus of a caesium atom.
  • Mass: A measure of the quantity of matter; related to gravitational pull and resistance to change in motion.