MOTION AND TIME

DISCOVERING MOVEMENT & MEASURING TIME

Introduction

Motion and time are closely related concepts. Understanding motion helps us study how objects move, while measuring time enables us to quantify and analyze motion.

1. Motion

What is Motion?

Motion occurs when an object changes its position with respect to its surroundings over time.

Types of Motion

1. Rectilinear Motion:
   • Straight-line motion.
   • Example: A car moving on a straight road.
2. Circular Motion:
   • Motion along a circular path.
   • Example: Hands of a clock, a merry-go-round.
3. Periodic Motion:
   • Motion that repeats after regular intervals.
   • Example: Pendulum of a clock, a swinging swing.

2. Measuring Motion

Distance and Displacement

• Distance: Total path covered by an object (scalar quantity).
• Displacement: Shortest path between the starting and ending point (vector quantity).

Speed

Speed is the distance covered by an object in a unit of time.

Formula:

Speed=Distance/Time

• Uniform Speed: Equal distances covered in equal intervals of time.
• Non-uniform Speed: Unequal distances covered in equal intervals of time.

Unit of Speed:

• SI Unit: meters per second (m/s)
• Other Units: kilometers per hour (km/h), miles per hour (mph).

Example

A car travels 150 km in 3 hours. Calculate its speed.

Speed=Distance/Time=150 km/3 hours=50 km/h

3. Time

Time is a fundamental aspect of motion. It helps in measuring how long an object takes to move from one place to another.

Instruments to Measure Time:

1. Sundials: Ancient devices using the shadow of the Sun.
2. Sand Clocks: Measure time with falling sand.
3. Modern Clocks: Digital and analog clocks.
4. Stopwatches: Measure time accurately in seconds.

4. Graphical Representation of Motion

Graphs help visualize motion.

Distance-Time Graph:

• Shows how distance changes with time.
• Straight Line: Uniform motion.
• Curved Line: Non-uniform motion.

Activity:

1. Record the time taken to walk a certain distance.
2. Plot the data on a graph to see the relationship between distance and time.

5. Units of Time and Speed

• Time:
  • SI Unit: second (s)
  • Other Units: minutes, hours, days.
• Speed:
  • SI Unit: meters per second (m/s).
  • Conversion: 1 km/h = 0.28 m/s.

6. Measuring Motion with a Simple Pendulum

A simple pendulum is a device used to study periodic motion.

Parts of a Pendulum:

• Bob: The weight at the end of the string.
• String: The thread that holds the bob.

Time Period:

• Time taken by the pendulum to complete one oscillation.

Experiment with a Pendulum

1. Hang a pendulum and let it swing.
2. Count the time it takes for 10 oscillations.
3. Calculate the time period:

Time Period=Total Time/Number of Oscillations

7. Practical Applications of Motion and Time

1. Traffic Systems: Speedometers and odometers in vehicles.
2. Sports: Stopwatches to measure athletes’ performance.
3. Astronomy: Study of planetary motion.

Examples for Better Understanding

1. A train travels 120 km in 2 hours. What is its speed?
   •  

Speed= 120 km/2 hours = 60 km/h

1. A pendulum completes 15 oscillations in 30 seconds. What is its time period?
   •  

Time Period =30 seconds/15 = 2 seconds

8. Fun Activity

Make Your Own Sundial

1. Take a stick and fix it in soft ground.
2. Mark the shadow of the stick at different times of the day.
3. Observe how the shadow moves as time passes.

Practice Questions

1. Define motion. Give two examples of periodic motion.
2. Explain the difference between uniform and non-uniform motion.
3. A cyclist covers 20 km in 40 minutes. Calculate the speed in km/h.
4. What is the time period of a pendulum if it completes 30 oscillations in 60 seconds?

Summary

Motion and time are essential aspects of our daily lives. By understanding motion types, measuring speed, and using tools like graphs and pendulums, we can better analyze and predict how objects move.

📝 Multiple Choice Questions

1. Motion occurs when an object:
A) Changes color
B) Changes position
C) Changes shape
D) Changes size

2. Motion depends on:
A) Distance only
B) Time only
C) Change in position over time
D) Shape

3. Which is an example of motion?
A) A stationary chair
B) A moving car
C) A wall
D) A book on a table

4. Rectilinear motion is:
A) Circular motion
B) Straight-line motion
C) Zig-zag motion
D) Random motion

5. Circular motion occurs in:
A) Straight path
B) Circular path
C) Zig-zag path
D) Random path

6. Example of circular motion:
A) Train on straight track
B) Clock hands
C) Walking person
D) Falling stone

7. Periodic motion repeats after:
A) Long time
B) Equal intervals
C) Random intervals
D) No time

8. Example of periodic motion:
A) Running car
B) Pendulum
C) Flying bird
D) Moving train

9. Distance is a:
A) Vector
B) Scalar
C) Force
D) Speed

10. Displacement is:
A) Total path
B) Shortest path
C) Random path
D) Circular path

11. SI unit of speed is:
A) km/h
B) m/s
C) m
D) s

12. Speed is:
A) Distance only
B) Time only
C) Distance ÷ Time
D) Time ÷ Distance

13. Uniform speed means:
A) Changing speed
B) Same distance in equal time
C) No movement
D) Unequal distance

14. Non-uniform speed means:
A) Same speed
B) No speed
C) Unequal distances in equal time
D) Equal distances

15. A car travels 100 km in 2 hours. Speed is:
A) 40 km/h
B) 50 km/h
C) 60 km/h
D) 70 km/h

16. Time is measured in:
A) Meter
B) Second
C) Kilogram
D) Newton

17. SI unit of time is:
A) Hour
B) Minute
C) Second
D) Day

18. Stopwatch is used to measure:
A) Distance
B) Speed
C) Time
D) Force

19. Sundial measures time using:
A) Water
B) Sand
C) Sun’s shadow
D) Wind

20. Distance-time graph for uniform motion is:
A) Curved
B) Straight line
C) Zig-zag
D) Circular

21. Distance-time graph for non-uniform motion is:
A) Straight
B) Curved
C) Flat
D) Horizontal

22. Speedometer measures:
A) Distance
B) Speed
C) Time
D) Force

23. Odometer measures:
A) Speed
B) Distance
C) Time
D) Force

24. 1 km/h equals:
A) 0.28 m/s
B) 2.8 m/s
C) 28 m/s
D) 0.028 m/s

25. A pendulum shows:
A) Circular motion
B) Rectilinear motion
C) Periodic motion
D) Random motion

26. Time period is:
A) Distance
B) Speed
C) Time for one oscillation
D) Total motion

27. Formula of time period:
A) Time × oscillations
B) Time ÷ oscillations
C) Oscillations ÷ time
D) Distance ÷ time

28. If 20 oscillations take 40 seconds, time period is:
A) 1 s
B) 2 s
C) 3 s
D) 4 s

29. Which is NOT a unit of time?
A) Second
B) Minute
C) Meter
D) Hour

30. Which is NOT a unit of speed?
A) m/s
B) km/h
C) m
D) mph

31. Speed depends on:
A) Distance and time
B) Time only
C) Distance only
D) Shape

32. Which motion is seen in a swing?
A) Rectilinear
B) Circular
C) Periodic
D) Random

33. Which device measures accurate time?
A) Sundial
B) Sand clock
C) Stopwatch
D) Stick

34. A train covers 120 km in 2 hours. Speed is:
A) 40 km/h
B) 50 km/h
C) 60 km/h
D) 70 km/h

35. Graph helps to:
A) Measure force
B) Visualize motion
C) Cook food
D) Produce energy

36. Which shows uniform motion?
A) Straight line graph
B) Curved graph
C) Circle
D) Zig-zag

37. Motion and time are:
A) Unrelated
B) Closely related
C) Opposite
D) Independent

38. A cyclist covers 30 km in 1 hour. Speed is:
A) 20 km/h
B) 25 km/h
C) 30 km/h
D) 35 km/h

39. Which instrument uses sand to measure time?
A) Clock
B) Stopwatch
C) Sand clock
D) Sundial

40. Which motion is seen in planets?
A) Circular
B) Rectilinear
C) Periodic
D) Both A and C

41. Distance is always:
A) Negative
B) Positive
C) Zero
D) Vector

42. Displacement can be:
A) Only positive
B) Positive or negative
C) Always zero
D) Always same

43. Motion of hands of clock is:
A) Rectilinear
B) Circular
C) Random
D) Zig-zag

44. Which is fastest unit?
A) m/s
B) km/h
C) cm/s
D) mm/s

45. A body at rest has:
A) Motion
B) Speed
C) No motion
D) High speed

46. Which is example of non-uniform motion?
A) Car at constant speed
B) Running person
C) Pendulum
D) Clock

47. Speed increases when:
A) Distance increases
B) Time increases
C) Distance decreases
D) Time decreases

48. A graph showing no motion is:
A) Straight slant line
B) Horizontal line
C) Curved line
D) Circle

49. Motion is relative to:
A) Time
B) Observer
C) Speed
D) Distance

50. Motion helps us to understand:
A) Shape
B) Movement
C) Color
D) Weight

✅ Answer Key (At the End)

1-B, 2-C, 3-B, 4-B, 5-B, 6-B, 7-B, 8-B, 9-B, 10-B
11-B, 12-C, 13-B, 14-C, 15-B, 16-B, 17-C, 18-C, 19-C, 20-B
21-B, 22-B, 23-B, 24-A, 25-C, 26-C, 27-B, 28-B, 29-C, 30-C
31-A, 32-C, 33-C, 34-C, 35-B, 36-A, 37-B, 38-C, 39-C, 40-D
41-B, 42-B, 43-B, 44-A, 45-C, 46-B, 47-A, 48-B, 49-B, 50-B