Chapter 13 – Motion and time

These NCERT Class 7 Science Chapter 13 notes explain how objects move and how motion is measured using time, distance, and speed. The chapter helps students understand that movement becomes meaningful only when it is measured and compared.

Motion and Time introduces different types of motion, methods of measuring time, and the concept of speed. It also explains distance–time graphs, which are important for understanding motion in a clear and visual way.

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1. Introduction: why motion and time are important

•  Many daily activities involve movement of objects.
•  To describe movement clearly, we need time, distance, and speed.
•  This chapter helps us measure and compare motion.
•  Movement becomes meaningful only when it is measured.

2. Motion

•  An object is in motion if it changes its position with time.
•  A moving bus, flying bird, and flowing river show motion.
•  If position changes with time, motion is present.

3. Types of motion

•  Rectilinear motion is movement along a straight line, like a train on a straight track.
•  Periodic motion repeats at equal intervals of time, like a pendulum or Earth’s rotation.
•  Circular motion is movement along a circular path, like fan blades.

4. Measuring time

•  Time helps measure the duration of events.
•  Earlier, people used natural events like sunrise and sunset.
•  Accurate measurement needs proper devices.

5. Units of time

•  Second (s), minute (min), and hour (h) are common units.
•  The SI unit of time is second.

6. Devices to measure time

•  Early devices include sundial, sand clock, and water clock.
•  Modern devices include clock and stopwatch.

7. Speed

•  Speed tells how fast an object moves.
•  It shows distance covered per unit time.
•  The formula is speed = distance ÷ time.

8. Units of speed

•  Common units are metre per second (m/s) and kilometre per hour (km/h).
•  Different situations use different speed units.

9. Distance–time relationship

•  More distance in less time means higher speed.
•  Less distance in more time means lower speed.

10. Uniform and non-uniform motion

•  Uniform motion covers equal distances in equal time intervals, like a car at constant speed.
•  Non-uniform motion covers unequal distances in equal time intervals, like a bus in traffic.

11. Distance–time graph

•  A distance–time graph shows the relation between distance and time.
•  Time is taken on the X-axis and distance on the Y-axis.

12. Interpretation of distance–time graph

•  A straight line shows uniform motion.
•  A curved line shows non-uniform motion.
•  A horizontal line shows the object is at rest.

13. Measuring speed using graph

•  A steeper line shows higher speed.
•  A gentle slope shows lower speed.

14. Odometer and speedometer

•  An odometer measures distance travelled.
•  A speedometer measures the speed of a vehicle.

15. Importance of measuring motion

•  Measuring motion helps in transport planning.
•  It ensures road safety.
•  It is useful in sports and daily life.

16. Important keywords with simple definitions

•  Motion – change in position with time.
•  Time – measure of duration of events.
•  Speed – distance covered per unit time.
•  Uniform motion – equal distance in equal time.
•  Non-uniform motion – unequal distance in equal time.
•  Distance–time graph – graph showing distance and time relation.

Understanding NCERT Class 7 Science Chapter 13 – Motion and Time is important to learn how movement is measured in science. The chapter clearly explains motion, speed, and graphs using simple examples from daily life.

These concepts are very useful for school examinations and foundation-level science preparation. Students should next read Chapter 14: Electric Current and its Effects to understand electricity and its applications.

FAQs

Q1. What is explained in NCERT Class 7 Science Chapter 13?
The chapter explains motion, time, speed, and distance–time graphs.

Q2. What is motion?
Motion is the change in position of an object with time.

Q3. What is speed?
Speed is the distance covered by an object per unit time.

Q4. What is uniform motion?
Uniform motion is when an object covers equal distances in equal intervals of time.

Q5. Why is NCERT Class 7 Science Chapter 13 important for exams?
It explains basic concepts of motion and graphs that are commonly asked in school and foundation-level exams.

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