Class 9 Science Describing Motion Around Us Notes

Class 9 Science Describing Motion Around Us Notes

Chapter 4: Describing Motion Around Us

🔹 1. What is Motion?

An object is said to be in motion if it changes its position with respect to time and surroundings.

👉 Example: A moving car, flying bird

🔹 2. What is Rest?

An object is at rest if its position does not change with respect to time and surroundings.

👉 Rest and motion are relative terms

🔹 3. Types of Motion

🟢 Rectilinear Motion

  • Motion in a straight line
    👉 Example: Train on straight track

🟡 Circular Motion

  • Motion along a circular path
    👉 Example: Clock hands, Earth around Sun

🔵 Periodic Motion

  • Motion repeated at regular intervals
    👉 Example: Swing, pendulum

🟣 Random Motion

  • No fixed path
    👉 Example: Dust particles in air

🔹 4. Distance and Displacement

📏 Distance

  • Total path covered by an object
  • Scalar quantity (only magnitude)

📍 Displacement

  • Shortest straight-line distance between initial and final position
  • Vector quantity (magnitude + direction)

⚠️ Key Difference:

  • Distance ≥ Displacement always

🔹 5. Speed

Speed = Distance / Time

👉 SI unit: m/s
👉 Scalar quantity

🔹 6. Types of Speed

🟢 Uniform Speed

  • Equal distances in equal time intervals

🔴 Non-uniform Speed

  • Unequal distances in equal time intervals

🔹 7. Velocity

Velocity = Displacement / Time

👉 Vector quantity (has direction)

🔹 8. Acceleration

Acceleration = Change in velocity / Time

👉 SI unit: m/s²

Types of Acceleration:

  • Positive acceleration (speed increases)
  • Negative acceleration (deceleration)

🔹 9. Graphical Representation of Motion

📊 Distance-Time Graph

  • Straight line → uniform motion
  • Curved line → non-uniform motion

📊 Velocity-Time Graph

  • Shows acceleration
  • Area under graph = displacement

🔹 10. Uniform Motion vs Non-uniform Motion

Uniform MotionNon-uniform Motion
Equal speedChanging speed
Constant velocityVariable velocity

🔹 11. Equations of Motion

  1. v = u + at
  2. s = ut + ½at²
  3. v² = u² + 2as

Where:
u = initial velocity
v = final velocity
a = acceleration
s = distance

🔹 12. Key Concepts for Exams

  • Motion depends on reference point
  • Distance is scalar, displacement is vector
  • Acceleration can be positive or negative
  • Graphs are very important

⚠️ Short Revision Line

👉 Motion = Change in position with time + reference point matters

Chapter 4: Describing Motion Around Us — MCQs (1–120)

🔹 Basic Concepts of Motion (1–30)

  1. Motion is defined as: A. change in shape B. change in position C. change in mass D. change in color
  2. Rest means: A. no change in position B. moving fast C. circular motion D. acceleration
  3. Motion is always measured with respect to: A. time B. reference point C. speed D. force
  4. Rest and motion are: A. absolute B. relative C. fixed D. constant
  5. Example of motion: A. tree B. moving car C. stone D. wall
  6. Example of rest: A. flying bird B. parked car C. running train D. flowing river
  7. Motion in straight line is called: A. circular B. rectilinear C. periodic D. random
  8. Motion along circular path is: A. rectilinear B. circular C. random D. oscillatory
  9. Repeated motion is: A. circular B. periodic C. rectilinear D. random
  10. Dust particles show: A. rectilinear B. random C. circular D. periodic motion
  11. SI unit of distance is: A. km B. m C. cm D. mm
  12. Distance is a: A. vector B. scalar C. force D. velocity
  13. Displacement is a: A. scalar B. vector C. mass D. time
  14. Distance is always: A. less than displacement B. equal or greater than displacement C. negative D. zero
  15. Displacement depends on: A. path B. direction C. time only D. mass
  16. Distance depends on: A. shortest path B. actual path C. direction D. force
  17. SI unit of displacement is: A. m B. km C. cm D. mm
  18. Zero displacement means: A. object moved B. no change in position C. fast motion D. circular motion
  19. Distance covered is always: A. zero B. positive C. negative D. vector
  20. Displacement can be: A. only positive B. positive or negative C. only zero D. only scalar
  21. Motion in a pendulum is: A. random B. periodic C. circular D. rectilinear
  22. Earth revolving around sun is: A. random B. circular C. rectilinear D. oscillatory
  23. A moving train on straight track shows: A. circular motion B. rectilinear motion C. random motion D. periodic motion
  24. A moving fan blade shows: A. rectilinear B. circular C. random D. oscillatory
  25. SI unit of time is: A. minute B. hour C. second D. day
  26. Motion of a ceiling fan is: A. random B. circular C. rectilinear D. periodic only
  27. A body is at rest if: A. moving fast B. position unchanged C. accelerating D. rotating
  28. Motion depends on: A. color B. reference point C. shape D. size
  29. A moving object may appear at rest to: A. all observers B. moving observer C. fixed observer D. none
  30. Reference point is also called: A. origin B. motion point C. rest point D. speed point

🔹 Speed, Velocity & Acceleration (31–70)

  1. Speed = A. distance/time B. displacement/time C. force/time D. mass/time
  2. Velocity = A. distance/time B. displacement/time C. speed×time D. force/mass
  3. Speed is a: A. vector B. scalar C. force D. displacement
  4. Velocity is a: A. scalar B. vector C. mass D. energy
  5. SI unit of speed is: A. m/s B. m²/s C. kg/m D. N
  6. Uniform speed means: A. changing speed B. constant speed C. zero speed D. negative speed
  7. Non-uniform speed means: A. constant speed B. changing speed C. zero motion D. circular motion only
  8. Acceleration = A. speed/time B. change in velocity/time C. distance/time D. force/time
  9. SI unit of acceleration: A. m/s B. m/s² C. km/s D. N/m
  10. Positive acceleration means: A. speed decreases B. speed increases C. no motion D. circular motion
  11. Negative acceleration is called: A. velocity B. deceleration C. speed D. force
  12. If velocity is constant, acceleration is: A. zero B. infinite C. negative D. positive
  13. Speed depends on: A. distance & time B. mass C. force D. shape
  14. Velocity depends on: A. direction B. color C. weight D. size
  15. Displacement/time gives: A. speed B. velocity C. force D. mass
  16. Distance/time gives: A. velocity B. speed C. acceleration D. force
  17. Acceleration occurs when: A. velocity changes B. mass changes C. time stops D. distance is zero
  18. A body moving in circle has: A. constant velocity B. changing velocity C. zero velocity D. constant speed only
  19. Uniform motion means: A. changing speed B. equal distance in equal time C. no motion D. circular motion
  20. Non-uniform motion means: A. equal distance B. unequal speed C. no motion D. rest
  21. Velocity can be: A. only positive B. positive or negative C. only zero D. only scalar
  22. Speed is always: A. negative B. positive C. zero only D. vector
  23. Acceleration can be: A. only positive B. positive or negative C. only zero D. scalar only
  24. Retardation means: A. increase in speed B. decrease in speed C. no motion D. circular motion
  25. Motion of car in traffic is: A. uniform B. non-uniform C. no motion D. circular
  26. A freely falling body has: A. zero acceleration B. constant acceleration C. variable speed only D. no motion
  27. Gravity produces: A. no motion B. acceleration C. rest D. force only
  28. SI unit of velocity is: A. m/s B. m/s² C. km² D. N
  29. Speedometer measures: A. acceleration B. speed C. force D. distance
  30. Odometer measures: A. speed B. distance C. force D. velocity
  31. Acceleration is change in: A. distance B. velocity C. force D. mass
  32. Negative acceleration reduces: A. mass B. speed C. time D. distance
  33. If object is at rest, speed is: A. 1 B. 0 C. infinite D. negative
  34. Circular motion has: A. constant velocity B. changing direction C. no motion D. no speed
  35. Velocity is defined with: A. only magnitude B. magnitude and direction C. only time D. only distance
  36. Speed is always: A. vector B. scalar C. force D. acceleration
  37. Acceleration depends on: A. velocity change B. mass only C. force only D. distance only
  38. Motion in a straight line is: A. circular B. rectilinear C. random D. periodic
  39. Speed is independent of: A. distance B. direction C. time D. magnitude
  40. Velocity changes if: A. direction changes B. mass changes C. time stops D. distance is zero

🔹 Graphs & Advanced Concepts (71–120)

  1. Distance-time graph slope gives: A. speed B. force C. mass D. acceleration
  2. Velocity-time graph slope gives: A. speed B. acceleration C. distance D. mass
  3. Area under velocity-time graph gives: A. acceleration B. displacement C. speed D. force
  4. Straight line in distance-time graph shows: A. rest B. uniform motion C. acceleration D. circular motion
  5. Curved graph shows: A. uniform motion B. non-uniform motion C. rest D. zero speed
  6. Flat line in distance-time graph means: A. motion B. rest C. acceleration D. velocity
  7. Slope in graph represents: A. direction B. rate of change C. mass D. force
  8. Distance-time graph for rest is: A. straight slant B. horizontal line C. curve D. circle
  9. Velocity-time graph for uniform motion is: A. curve B. straight horizontal line C. zigzag D. circle
  10. Acceleration is zero when velocity is: A. changing B. constant C. negative D. zero only
  11. Motion can be described using: A. graphs B. colors C. smell D. taste
  12. Motion in space is relative to: A. object B. reference point C. force D. mass
  13. Displacement can be zero even if distance is: A. zero B. non-zero C. negative D. infinite
  14. Round trip displacement is: A. zero B. distance C. speed D. acceleration
  15. Speed has no: A. magnitude B. direction C. time D. unit
  16. Velocity has: A. no direction B. direction C. no time D. no magnitude
  17. Acceleration is rate of change of: A. speed B. velocity C. distance D. mass
  18. A car moving in circle has: A. constant velocity B. changing direction C. no speed D. rest
  19. Motion of Earth is: A. random B. circular C. rectilinear D. stationary
  20. Motion of pendulum is: A. random B. periodic C. circular D. straight
  21. Uniform motion graph is: A. curve B. straight line C. circle D. zigzag
  22. Non-uniform motion graph is: A. straight B. curve C. flat D. horizontal
  23. Acceleration is zero when: A. velocity changes B. velocity constant C. distance changes D. force applied
  24. Velocity is zero when object is: A. moving B. at rest C. accelerating D. rotating
  25. Distance-time graph slope is: A. velocity B. speed C. acceleration D. force
  26. Motion in zigzag path is: A. rectilinear B. random C. circular D. periodic
  27. A moving fan shows: A. rectilinear B. circular C. random D. straight
  28. SI unit of acceleration is derived from: A. speed B. velocity/time C. force D. mass
  29. Motion depends on: A. observer B. color C. weight D. size
  30. Speed is ratio of: A. time/distance B. distance/time C. force/mass D. velocity/time
  31. Velocity is ratio of: A. displacement/time B. distance/time C. force/time D. mass/time
  32. Acceleration increases when: A. velocity changes faster B. time increases C. distance decreases D. mass decreases
  33. Motion of bicycle is: A. uniform always B. non-uniform mostly C. circular D. rest
  34. Graph shows motion in: A. numbers B. visual form C. sound D. smell
  35. Slope indicates: A. direction B. steepness C. mass D. force
  36. Faster motion has: A. low speed B. high speed C. zero speed D. negative speed
  37. Slower motion has: A. high speed B. low speed C. zero time D. no distance
  38. Rest means: A. motion B. no motion C. acceleration D. force
  39. Motion of planets is: A. random B. circular C. straight D. no motion
  40. Speed is measured by: A. thermometer B. speedometer C. barometer D. ammeter
  41. Distance cannot be: A. zero B. negative C. positive D. large
  42. Displacement can be: A. negative B. positive or negative C. zero only D. none
  43. Motion is always relative to: A. sun B. observer C. earth D. air
  44. Graph helps to understand: A. smell B. motion C. color D. sound
  45. Acceleration is zero in: A. uniform motion B. rest C. both A and B D. circular motion
  46. Uniform speed means: A. changing B. constant C. zero D. random
  47. Velocity includes: A. only magnitude B. magnitude and direction C. only direction D. none
  48. Motion of train is: A. always uniform B. often non-uniform C. circular D. random
  49. Free falling object has: A. zero acceleration B. constant acceleration C. no motion D. random motion
  50. Displacement is: A. scalar B. vector C. force D. mass

Answer Key (1–120)

QAQAQAQAQA
1B21B41B61B81B
2B22B42A62B82B
3B23B43A63B83B
4B24B44A64B84A
5B25C45B65B85B
6B26B46B66B86B
7B27B47A67A87B
8B28B48B68B88B
9B29B49B69B89B
10B30A50B70A90B
11B31B51B71B91B
12B32B52B72B92B
13B33B53B73B93B
14B34B54B74B94B
15B35B55B75B95A
16B36B56B76B96B
17B37B57B77B97B
18B38B58A78B98B
19B39B59B79C99A
20B40B60B80B100C

Graph-Based MCQs (1–50)

🔹 Distance–Time Graph (1–25)

  1. Slope of distance–time graph gives: A. acceleration B. speed C. force D. mass
  2. A straight line in distance–time graph shows: A. rest B. uniform motion C. acceleration D. random motion
  3. A horizontal line in distance–time graph shows: A. motion B. rest C. acceleration D. velocity
  4. Curved distance–time graph shows: A. uniform motion B. non-uniform motion C. rest D. zero speed
  5. Steeper slope means: A. slow speed B. high speed C. no speed D. rest
  6. Less steep slope means: A. higher speed B. lower speed C. no motion D. acceleration
  7. Distance–time graph cannot be: A. straight B. curved C. horizontal D. circular
  8. If distance increases uniformly, graph is: A. curve B. straight line C. zigzag D. circle
  9. If object is at rest, graph is: A. upward line B. horizontal line C. curve D. slope
  10. Distance-time graph is always: A. straight B. graphical representation C. force diagram D. vector
  11. Uniform motion is shown by: A. curved line B. straight line C. circle D. zigzag
  12. Non-uniform motion is shown by: A. straight line B. curved line C. horizontal line D. no graph
  13. Slope of graph represents: A. mass B. speed C. force D. time
  14. If slope is zero, object is: A. moving fast B. at rest C. accelerating D. rotating
  15. Equal distance in equal time gives: A. curved graph B. straight line C. no graph D. circle
  16. Distance-time graph shows relation between: A. speed & force B. distance & time C. mass & velocity D. force & time
  17. Graph for constant speed is: A. curve B. straight line C. zigzag D. circle
  18. Increasing slope means: A. decreasing speed B. increasing speed C. no speed D. rest
  19. Decreasing slope means: A. acceleration B. deceleration C. rest D. uniform motion
  20. Horizontal line means: A. motion B. rest C. acceleration D. force
  21. A graph with changing slope shows: A. uniform motion B. non-uniform motion C. rest D. no time
  22. Distance-time graph is plotted with: A. time on x-axis B. distance on x-axis C. force on x-axis D. mass on x-axis
  23. Distance is plotted on: A. x-axis B. y-axis C. both D. none
  24. Time is plotted on: A. x-axis B. y-axis C. both D. none
  25. Straight line graph indicates: A. changing speed B. constant speed C. no motion D. circular motion

🔹 Velocity–Time Graph (26–50)

  1. Slope of velocity-time graph gives: A. speed B. acceleration C. force D. mass
  2. Area under velocity-time graph gives: A. acceleration B. displacement C. speed D. force
  3. Straight horizontal line in v–t graph shows: A. acceleration B. uniform velocity C. rest D. force
  4. Rising line in v–t graph shows: A. deceleration B. acceleration C. rest D. constant speed
  5. Falling line in v–t graph shows: A. acceleration B. deceleration C. rest D. force
  6. Zero slope in v–t graph means: A. acceleration B. no acceleration C. force D. mass
  7. Curved v–t graph shows: A. uniform motion B. non-uniform acceleration C. rest D. no motion
  8. Velocity-time graph is used to find: A. force B. acceleration C. color D. mass
  9. Uniform velocity is shown by: A. curved line B. horizontal straight line C. circle D. zigzag
  10. Acceleration increases when slope: A. decreases B. increases C. becomes zero D. negative
  11. Deceleration is shown by: A. rising graph B. falling graph C. horizontal graph D. circle
  12. Area under graph represents: A. speed B. displacement C. force D. mass
  13. Velocity-time graph axes are: A. distance-time B. velocity-time C. force-time D. mass-time
  14. Time is always on: A. y-axis B. x-axis C. both D. none
  15. Velocity is on: A. x-axis B. y-axis C. both D. none
  16. Constant acceleration graph is: A. straight line B. curve C. horizontal D. zigzag
  17. Zero velocity means graph lies on: A. x-axis B. y-axis C. curve D. slope
  18. Increasing velocity shows: A. downward slope B. upward slope C. horizontal line D. circle
  19. Decreasing velocity shows: A. upward slope B. downward slope C. horizontal D. no graph
  20. Flat v–t graph means: A. acceleration B. constant velocity C. rest D. force
  21. Steep slope in v–t graph means: A. low acceleration B. high acceleration C. rest D. zero speed
  22. Velocity-time graph is also called: A. motion graph B. speed graph C. force graph D. mass graph
  23. Acceleration is: A. slope of distance graph B. slope of velocity graph C. area under distance graph D. none
  24. Displacement from graph is: A. slope B. area under curve C. height D. width
  25. Motion graphs help to study: A. force only B. motion behavior C. color change D. mass only

Answer Key (Graph-based MCQs 1–50)

QAQAQAQAQA
1B11B21B31B41A
2B12B22A32B42A
3B13B23B33B43B
4B14B24A34B44B
5B15B25B35B45B
6B16B26B36B46B
7D17B27B37B47A
8B18B28B38B48B
9B19B29B39B49B
10B20B30B40B50B