Page 110 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

Now, let's see how time, another quantity is measured.
Time

The given picture shows the shadow cast by the flag pole of your school
in the morning, at noon and in the evening.

Fig 8.14 (a) Fig 8.14 (b) Fig 8.14 (c)
Morning Noon Evening

Of these, at what time is the shadow of the least length
cast?
What may be the reason?
Have you ever tried to ascertain the time by observing
the difference in the length of shadows?

Our ancestors used to determine approximate time by
observing the shadow of objects. They used the sundial as
well. Suggest a method to make a sundial.
Is the sundial you have made, suitable for use at night? sundial

What might have been the measures taken by our Fig 8.15
ancestors to ascertain time at night? Discuss.

By what name is the time from one noon to the next noon Solar day
referred?
A day or a solar day is the
For measuring time intervals less than a day, a day is
time period from one noon
divided into twenty four equal parts. What is each of to the next noon.
this duration of time referred as?
Aren't you aware that the time obtained by dividing this
part into 60 equal parts is a minute?

The time interval obtained by dividing a minute into 60
equal parts is the basic unit of time. What is it known
as?
How many seconds make a day (one solar day)?

Basic Science VIII 109