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Grade 7 | Science | Simple Pendulum, Motion and Time, Olympiad, CBSE, ICSE, Maths Olympiad, Science Olympiad, English Olympiad
Simple pendulumIn order to understand the use of a simple pendulum in the measurement of time, we need to understand periodic motion.
Periodic motion is the motion that repeats itself at equal intervals of time. This motion is commonly used in clocks and watches.
A simple pendulum has a weight (bob) tied on one end of the string which is long, fine and weightless, attached to a rigid support.
The time period of the pendulum is the total time to complete one oscillation. It depends upon the length of the string with which the bob is suspended. It has been observed that for a particular pendulum length the time period doesn't change and it is taken as constant. This has led to the formation of pendulum clocks.
Measurement of times ( In ancient time)1. Sundial
The sundial was based on the observation that the position and length of the shadow cast by an object change with the time during the daytime. It is made up of a horizontal circular board with a triangular plate of metal which is fixed vertically on it and kept along the north-south direction. The plate casts its shadow on the board. So wherever the edge of the shadow formed fall during the daytime. This position of the shadow is used to Mark the time of the day.
2. Hourglass
Hourglass or sand clock consists of two rounded glass bulbs which are connected to each other by a narrow neck of glass. Usually, it works on the principle that sand from the upper glass bulb falls into the lower glass bulb in a fixed time which they utilized for time measurement.
3. Water clock
Water clock was a unique time measuring instrument which was based on the principle of regulated flow of water. In this device time taken for the container to empty up to different levels was measured.
Measurement of time ( In modern times)
1. Watches
Clocks with pendulum were the first instrument used for measuring the time. Galileo contributed to the formation of pendulum watches as he discovered that the time of oscillation of a pendulum of a given length js always constant. A pendulum clock swings continuously under the action of a spring. And this spring controls the hands of the clocks.
2. Atomic clock
It the most accurate of all the clocks ever made in the history of clocks. It is well maintained at the national physical laboratory (NPL) at Delhi, which is used to provide beeps before the morning news. It is said that the clock is accurate up to the millionth part of a second.
3. Stopwatch
Stopwatches are generally used by athletes and it measures time up to 1/10 of a second accurately.
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