Measurement of Length, Mass & Time
Measurement plays a crucial role in physics as it allows us to describe physical quantities
accurately. Three of the most commonly measured quantities in daily life and science are
length, mass, and time.
Measurement of Length
Length is the distance between two points. It is used to measure the size of objects,
distance traveled, and dimensions of physical systems.
The SI unit of length is the metre (m).
Common Instruments for Measuring Length
- Metre scale / ruler – for small lengths
- Measuring tape – for longer distances
- Vernier calipers – for precise measurements
- Screw gauge – for very small thicknesses
Multiples and Submultiples of Metre
- 1 kilometre (km) = 1000 m
- 1 centimetre (cm) = 0.01 m
- 1 millimetre (mm) = 0.001 m
Measurement of Mass
Mass is the quantity of matter present in an object. It remains constant regardless of
the object's location.
The SI unit of mass is the kilogram (kg).
Instruments Used to Measure Mass
- Beam balance
- Digital weighing machine
- Physical balance
Mass Conversions
- 1 kilogram (kg) = 1000 grams (g)
- 1 gram (g) = 0.001 kg
Measurement of Time
Time is the measure of the duration of events or the interval between two events.
The SI unit of time is the second (s).
Devices Used to Measure Time
- Clock and wristwatch
- Stopwatch
- Atomic clock (most accurate)
Time Conversions
- 1 minute = 60 seconds
- 1 hour = 60 minutes = 3600 seconds
Importance of Accurate Measurement
- Helps in scientific experiments
- Ensures accuracy in engineering and construction
- Essential in daily life activities
Q1. The SI unit of length is:
A) centimetre
B) metre
C) kilometre
D) millimetre
Answer: B
Q2. Which instrument is best suited to measure the thickness of a wire?
A) Metre scale
B) Measuring tape
C) Vernier calipers
D) Screw gauge
Answer: D
Q3. The SI unit of mass is:
A) gram
B) kilogram
C) tonne
D) milligram
Answer: B
Q4. Which of the following is the most accurate time-measuring device?
A) Wristwatch
B) Stopwatch
C) Pendulum clock
D) Atomic clock
Answer: D
Q5. 1 kilometre is equal to:
A) 100 m
B) 500 m
C) 1000 m
D) 10,000 m
Answer: C
One-Page Revision: Measurement of Length, Mass & Time
SI Units
- Length → metre (m)
- Mass → kilogram (kg)
- Time → second (s)
Measuring Instruments
- Length → Ruler, Measuring tape, Vernier calipers, Screw gauge
- Mass → Beam balance, Digital balance
- Time → Clock, Stopwatch, Atomic clock
Important Conversions
- 1 km = 1000 m
- 1 cm = 0.01 m
- 1 kg = 1000 g
- 1 min = 60 s
- 1 hour = 3600 s
Key Points
- Mass is independent of location
- Atomic clocks are the most accurate
- Correct instrument selection improves accuracy
