Page 172 - Science Class 07

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i In ancient times, people got a rough idea of time on the basis of some natural events like
sunrise, sunset, etc.
i Sundials were based on the change in the length of the shadow with change in position of
the sun.
i The famous king of Jaipur, Maharaja Jai Singh, had built many sundials in different cities of
India during 18th century.
i Sand clock was another set up which was used to know the time.
i Pendulum was perhaps, the first modern time measurement device invented by a Dutch
scientist, Huggins in 1656.
i The quartz clock was invented in 1926 to know the time more accurately.
i The quartz clock works on the basis of the vibration of certain crystals.

i Digital clocks display time in digits.
i A stopwatch is used to know the time taken in completing a piece of work.
i When an object moves with a constant speed and covers equal distance in equal interval of
time, this motion is called uniform motion.

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A. Tick (3) the correct op on.
1. In which of the following places a sundial is situated?
(a) Ahmedabad (b) Lucknow
(c) Delhi (d) Kanpur
2. How many mes the minute hand of a clock makes a complete round in
1 hour 30 minutes?
(a) 60 mes (b) 110 mes
(c) 90 mes (d) 30 mes

3. Which of the following is the most advanced me measurement device?
(a) Sundial (b) Sand Clock
(c) Pendulum (d) Digital Clock

4. How many years come in one millennium?
(a) 10 years (b) 100 years
(c) 1000 years (d) 10,000 years
5. A car covers a distance of 180 km in 3 hours. What is the speed of the car?

(a) 60 km/hour (b) 180 km/hours
(c) 75 km/hour (d) None of these
B. Fill in the blanks.

1. The king of Jaipur, _____________ built sundials in many city of India.
2. Pendulum was invented by a Dutch scien st, _____________ in 1656.

172 Science-7