Measurement of Time and Motion PDF Class 7 Notes

Measurement of Time and Motion: Time and motion are an essential part of our life. Time indicates when to wake up, go to school, or when to have lunch or dinner, and when to sleep. Motion is related to how we move and how other things are moving – like cars moving on the road and a fan rotating in a room.

Ancient people used natural methods for measuring time. They saw the position of the sun in the sky and the shadows it cast during the day. People later invented clocks and watches to measure time.

Huygen’s Pendulum Clock

The pendulum clock was invented by a Dutch scientist, Christiaan Huygens, in 1656. It was the first clock to give the correct time. The pendulum is a piece of metal hanging from the ceiling, which moves to and fro at a fixed speed.

The time period is the time taken by the pendulum to complete one to-and-fro motion. It takes the same time to move one way and come back.

SI Unit of Time

The SI unit of time is second (s). It is used as the unit of time all over the world. Minutes, hours, and days are the bigger units, and milliseconds, microseconds, etc., are the smaller units of time.

1 minute = 60 seconds

1 hour = 60 minutes = 3,600 seconds

Interesting Facts of Time

Time has been measured in many creative ways since ancient times. Here are some interesting facts:

• Samrat Yantra is the world’s largest stone sundial which is around 300 years old.
• It is in Jantar Mantar, Jaipur, Rajasthan, which is a UNESCO World Heritage Site.
• The Samrat Yantra is 27 metres in height and measures time from the shadow of the sun.
• The ancient Indians also used sundials and water clocks for keeping time.
• Kautilya’s Arthashastra and the works of Varahamihira mention the measurement of time from the shadow of a vertical stick.

Speed

Speed is the measure of how fast or slow an object moves. It is measured by the distance it covers in a given time.

Formula: Speed = Distance ÷ Time

For example, if a car travels 100 km in 2 hours, then the speed of the car is 50 km/h.

Uniform and Non-Uniform Linear Motion

Uniform Motion: If an object covers the same distance in equal intervals of time, then the motion of the object is said to be uniform. Example – a car travelling at 60 km/h and not changing its speed.

Non-Uniform Motion: If an object covers unequal distances in equal intervals of time, then the motion of the object is said to be non-uniform. Example – a car driving in traffic.