MEASUREMENT IN PHYSICS

MEASUREMENT IN PHYSICS (CONT)

Measurement of area and volume
Concept & measurement of time and ways of measuring time.

Table of Contents

MEASUREMENT OF VOLUME

Volume of liquid objects is measured using instruments such as cylinder, burette, pipette, eureka can, etc. For regular solid objects, their volume could be determined using their mathematical formula.

S/N	Solid Object	Formula for Volume
1.	Cube
2.	Cuboid
3.	Cylinder
4.	Cone
5.	Sphere

The S.I. unit of volume is metre cube .

MEASUREMENT OF AREA

The area of a solid object could be determined using mathematical formulae after determining the two dimensions of the object.

S/N	Solid Object	Formula for Area
1.	Triangle
2.	Rectangle
3.	Square
4.	Parallelogram
5.	Trapezium

The S.I. unit of volume is metre square .

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WORKED EXAMPLES

Find the volume of a cylinder of diameter 12cm and height 15cm.

Solution:

Now,

2.What is area of a triangular card board of base 6cm and height 4cm?

Solution:

Evaluation:

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Calculate the volume of a rectangular prism of dimension 7cm by 3.5cm by 1.5cm.
A cube has an edge of 0.8cm. Find its volume.

CONCEPT & MEASUREMENT OF TIME, AND WAYS OF MEASURING TIME

You must have heard the following statements made about time:

“Time and tide waits for no man”
“Time is business”
“There is time for everything: time to sow and time to reap, time to laugh and time to cry, time to go to bed and time to wake up” and so on

Time is very important in our daily activities. Many people have failed in one area or the other because of mismanagement of time. In Physics time is very important. Wrong timing can lead to wrong observations, results and wrong conclusions.

What then is time. Time may be considered as the interval between two successive events. It is a fundamental quantity. Its S.I unit is seconds.

Ways of measuring time

Time as mentioned earlier is very important. That is why early men developed various means of measuring time. They used the sun to tell time. Even today people still use the position of the sun to determine time. Other devices they developed and used are:

The water clock
The sand clock
The primitive Sundials

Today, we have better time-measuring devices that measure time more accurately than the above mentioned devices. Some of them are:

The stop watch which is the standard instrument for measuring time in the laboratory
The wrist watch
The modern pendulum clock
The wall clock

It is worthy of note that:

60 seconds makes one minute
60 minutes makes one hour
24 hours makes one day
365/366 days makes one year
10 years makes a decade
100 years makes a century/centenary
1000 years makes a millennium

Calculations on time

Example 1

How many seconds are there in 2 hours 15 minutes?

Solution

Since 60 seconds makes 1 minute and 60 minutes makes 1 hour, 1 hour will have 60 x 60 seconds. 2 hours will have 60 x 60 x2 seconds = 7200seconds.

15 minutes will have 60 x 15 seconds = 900 seconds

Therefore 2 hours 15 minutes will have (7200 + 900) seconds = 8100 seconds

Example 2

If it takes a pendulum bob 32 seconds to complete 20 oscillations, what is the period of oscillation of the bob?

Solution

Period ( T ) is time ( t ) taken for the bob to complete an oscillation.

i.e T = t

number of oscillations

T = 32

= 1.6 seconds

Evaluation

What is the standard instrument for measuring time in the laboratory?
Mention 2 examples each of modern and olden days time-measuring devices you know.

GENERAL EVALUATION: