Measurements
Measurements play a very important role in Physics. We measure different quantities using
different measuring instruments in different units.
A Physical quantity consists of a magnitude and unit
e.g Length = 50 cm
SI Unit means systeme international.
Measuring
Physical
instrument
quantities
Length,
distance,
width
Common Units
used
SI Unit
Conversion factors
1 m=……cm
3 km= ……..m
500 m=…….km
2 cm=………..mm
Seconds (s),
Minutes (mins)
1 hr =…….mins=……..s
1 day =……hour
=………mins=………..s
Mass
thermometer
Measuring cylinder
Exercises
1 Which one of the following is a physical quantity? A Kelvin
2.What is the S.I. unit of mass?
B Kilogram C Metre
D Volume
A kelvin (K) B kilogram (kg) C metre (m) D second (s)
3.Which instrument is used to measure length? A A ruler B A clock C A balance D A thermometer
Measurement of Length
Length of pencil =...............................
Length of arrow =...............................
Measurement of length
(i)
Use Fig. 5.1 to calculate the diameter of one steel ball. Show all your workings.
(ii)
(ii) Suggest a reason why Neel uses wooden blocks in the measurement.
……………………………………………………………………………………………………………………………………
Explain why the student uses 3 ball instead of 1 ball
(iii)
A student measures the diameter of a coin using the arrangement shown in
The arrangement used by the student is faulty. What type of error is shown in Fig. 3.1?
…………………………………………………………………………………………………………………………………………………[1]
…………………………………………………………………………………………………………………………………………………..
ii) What can the student do to avoid this error?
Tick (✓) the correct answer.
1.Measure the diameter of 10 coins instead
2.Place his eyes opposite to the mark being read
3.Fix the coin between two clearly visible division and substract the two readings[1]
iii) explain how you can you measure the circumference of the coin using a piece of thread and a
ruler?
Measurement of volume
1. Where should you place your eye to
read the volume
A
2. How is the error due to the wrong
positioning of the eye called?
B
3.How do you avoid this type of error ?
C
3.What is the volume of liquid shown?
The surface of the liquid is curved. The curved curface of a
liquid is called ………………………………….
A measuring cylinder is used to measure the
volume of a stone. Fig. 3.1 below shows the
measuring cylinder containing 44 cm3 of
water. Fig. 3.2 shows the same measuring
cylinder after a stone is lowered completely
into it.
a) Determine the volume of the stone. Volume
= ...................................... cm3 [2]
b) Give two precautions you should take to
determine the volume of the stone in Fig. 3.2
as accurately as possible.
Name the method used in Fig. 5.4.