1. Measurement and Units
​Understanding how to measure and calculate physical quantities is fundamental in science. The following are commonly measured quantities and their associated units:
Measurement Quiz

Measurement Quiz

1. The standard unit of mass in the SI system is the kilogram (kg).

True
False

2. A metre stick can be used to measure time.

True
False

3. The prefix "milli-" means one thousandth (10-3) of a unit.

True
False

4. Volume is measured in square metres (m²).

True
False

5. When measuring the length of an object, you should always start at the 1 cm mark on a ruler to avoid errors.

True
False
2. Common Calculations
​Density:
  • Formula:
    Density= Mass/Volume​
  • Example: If a cube has a mass of 20 g and a volume of 10 cm³, its density is:
    Density= 20/10 = 2 g/cm3
Speed:
  • Formula:
    Speed= Distance/Time​
  • Example: A car travels 100 km in 2 hours. Its speed is:
    Speed=100/2=50 km/h
​Acceleration:
  • Formula:
    Acceleration=Change in Speed/Time​
  • Example: If a car's speed changes from 20 m/s to 40 m/s in 5 seconds:
    Acceleration=(40−20)/5= 4 m/s2
Force:
  • Formula:
    Force=Mass×Acceleration
  • Example: A 10 kg object accelerates at 3 m/s². Its force is:
    Force=10×3=30 N.
Electrical Power:
  • Formula:
    Power=Voltage×Current
  • Example: A device uses 12 volts and 2 amps. Its power is:
    Power=12×2=24 W.

3. Tips for Measurement
  • Always use the correct instrument for the quantity you are measuring.
  • Ensure instruments are calibrated properly (e.g., zeroing a balance).
  • Record measurements to the appropriate level of precision.
  • Repeat measurements and calculate an average for more accurate results.

4. Applications in Everyday Life
  • Density: Explains why some objects float while others sink.
  • Speed: Used to calculate travel times and monitor traffic safety.
  • Force: Helps engineers design bridges and buildings.
  • Electrical Power: Used to calculate energy usage and costs in homes and industries.

Length, Time, Speed and Acceleration

Measuring length
Picture
Micrometer Screw
Picture
Digital Caliper
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Rule
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Trundle Wheel
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Opisometer

Area, Volume, Mass and Density

Density Tower
The density of an object is calculated by dividing it's mass by it's volume.
The density of a liquid is a measure of how heavy it is for the amount measured.
In these towers, equal volumes of various liquids were measured, the liquid that weighs more is more dense.
This activity uses several types of liquids to determine which is more dense.
Lighter liquids are less dense so they float on top.

Why do some liquids weigh more than others?
Like solids, liquids are made up of different numbers of atoms and molecules.
In some liquids, these atoms and molecules are packed tightly together resulting in a denser heavier liquid e.g. syrup.

Force

To the right is a video demonstrating Electrostatic Force in action!
When we rub a plastic pen up and down the sleeve of our jumper and then hold the pen near pieces of paper, the paper is attracted to the pen. This happens because the charged pen induces an opposite charge in the paper and as opposite charges attract, the paper sticks to the pen.

Electrical Current, Potential Difference, Resistance and Electrical Power

Electrical Current, Potential Difference, Resistance, and Electrical Power
1. Electrical Current
  • Definition: Flow of electric charge (electrons) through a conductor.
  • Unit: Amperes (A).
  • Measured By: Ammeter.
  • Example: A 2 A current means a certain amount of charge passes every second.

2. Potential Difference (Voltage)
  • Definition: Energy provided to move charge between two points in a circuit.
  • Unit: Volts (V).
  • Measured By: Voltmeter.
  • Formula: V=Energy/Charge​.
  • Example: A 9V battery provides 9 units of energy for each unit of charge.

3. Resistance
  • Definition: Opposition to current flow in a material.
  • Unit: Ohms (Ω).
  • Measured By: Ohmmeter.
  • Formula: R=VoltageCurrent​.
  • Example: A 10 V circuit with 2 A current has R=5 Ω.

4. Electrical Power
  • Definition: Rate at which electrical energy is used.
  • Unit: Watts (W).
  • Formula: P=Voltage×Current.
  • Example: A device using 12V and 2A has P=24 W

Questions:

Q1: What instrument is used to measure length?
A: A ruler, measuring tape, or vernier calipers.
Q2: What is the unit of measurement for mass?
A: Kilogram (kg) or gram (g).
Q3: What is the formula for calculating density?
A: Density = Mass ÷ Volume.
Q4: How do you calculate speed?
A: Speed = Distance ÷ Time .
Q5: What unit is used to measure temperature?
A: Degrees Celsius (°C) or Kelvin (K).
Q6: How do you calculate force?
A: Force = Mass × Acceleration.
Q7: What is the formula for electrical power?
A: Power = Voltage × Current.
Q8: What instrument is used to measure current in a circuit?
A: An ammeter.
Q9: What unit is used to measure potential difference (voltage)?
A: Volt (V).
Q10: How is resistance calculated?
A: Resistance = Voltage ÷ Current 
Q11: What instrument measures time in experiments?
A: A stopwatch or clock.
Q12: What is the unit for measuring area?
A: Square metres.
Q13: How is volume measured in a laboratory?
A: Using a measuring cylinder, graduated beaker, or pipette.
Q14: What is the unit for measuring acceleration?
A: Metres per second squared.
Q15: How do you calculate the volume of a rectangular box?
A: Volume = Length × Width × Height.