Chapter 5: Measurement of Length and Motion

Introduction

Measuring length and understanding motion are fundamental concepts in science. Everything around us moves, and accurate measurement helps in experiments, daily life, and understanding the world.

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1. Measurement of Length

• Length is the distance between two points.
• Standard units of length:
  • Meter (m) – basic unit
  • Centimeter (cm), Millimeter (mm), Kilometer (km) – other units

Instruments to Measure Length:

• Ruler – for small lengths
• Measuring tape – for longer lengths
• Vernier caliper – for very precise measurements
• Odometer – for measuring distances travelled

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2. Measurement of Motion

• Motion: Change in the position of an object with time.
• Types of motion:
  1. Linear motion – along a straight line (e.g., train on tracks)
  2. Rotational motion – around an axis (e.g., fan blades)
  3. Oscillatory motion – back and forth (e.g., pendulum)
• Speed = Distance ÷ Time
  • Unit: meters per second (m/s) or km/h

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3. Tools and Methods

• Stopwatch – to measure time
• Measuring tape/ruler – to measure distance
• Motion sensor – in laboratories for precise motion study

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4. Key Points to Remember

• Length is measured using standard units.
• Motion is described by distance, speed, and direction.
• Speed = Distance ÷ Time
• Motion can be uniform (constant speed) or non-uniform (changing speed).

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Questions

1. Very Short Answer (1 mark)

1. What is length?
2. Name two units of length.
3. What is motion?
4. Name one instrument to measure short lengths.
5. Name one instrument to measure long distances.
6. What is the formula for speed?
7. Give an example of rotational motion.
8. Give an example of oscillatory motion.
9. What is the SI unit of length?
10. What instrument measures time in motion experiments?

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2. Multiple Choice Questions (MCQ)

1. Which is the SI unit of length?
   a) cm
   b) mm
   c) meter
   d) km
2. Speed is calculated as:
   a) Distance × Time
   b) Distance ÷ Time
   c) Time ÷ Distance
   d) Distance + Time
3. Which motion is back-and-forth?
   a) Linear
   b) Oscillatory
   c) Rotational
   d) None
4. Which instrument is used for very precise measurement of small lengths?
   a) Ruler
   b) Measuring tape
   c) Vernier caliper
   d) Odometer
5. A train moving along a straight track shows:
   a) Linear motion
   b) Rotational motion
   c) Oscillatory motion
   d) Random motion

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3. Fill in the Blanks

1. The basic unit of length is __________.
2. Speed is equal to __________ divided by __________.
3. Fan blades show __________ motion.
4. Pendulum shows __________ motion.
5. Long distances are measured using __________.

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4. True/False Type

1. Motion is the change in position of an object. (True/False)
2. Kilometer is smaller than meter. (True/False)
3. Stopwatch is used to measure time. (True/False)
4. Speed is measured in m/s or km/h. (True/False)
5. Motion can be uniform or non-uniform. (True/False)

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5. Short Answer Questions (2–3 marks)

1. Define motion in your own words.
2. Name three types of motion with examples.
3. What is a ruler used for?
4. How do we measure speed?
5. Give an example of uniform motion and non-uniform motion.

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6. Long Answer Questions (4–5 marks)

1. Explain the different units of length and their conversions.
2. Define motion and explain its types with examples.
3. What is speed? How is it calculated? Give examples.
4. Name instruments used to measure length and motion and explain their use.
5. Explain the difference between uniform and non-uniform motion.

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7. Higher-Order Thinking (HOT) & Application

1. A car travels 120 km in 2 hours. Calculate its speed.
2. How would you measure the length of a curved path in a playground?
3. A pendulum completes 20 oscillations in 40 seconds. Find the time period of one oscillation.

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8. Passage-Based Questions

Read the passage and answer:
Motion is the change in position of an object over time. It can be linear, rotational, or oscillatory. Measuring length and time accurately helps us study motion and calculate speed.

1. What is motion?
2. Name the three types of motion.
3. How is speed calculated?
4. Why is measuring length important in motion studies?

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Answer

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1. Very Short Answer

1. Distance between two points.
2. Meter, centimeter, millimeter, kilometer
3. Change in position of an object over time.
4. Ruler
5. Measuring tape, odometer
6. Speed = Distance ÷ Time
7. Fan blades
8. Pendulum
9. Meter
10. Stopwatch

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2. MCQ Answers

1. c) meter
2. b) Distance ÷ Time
3. b) Oscillatory
4. c) Vernier caliper
5. a) Linear motion

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3. Fill in the Blanks

1. meter
2. distance, time
3. rotational
4. oscillatory
5. measuring tape

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4. True/False

1. True
2. False
3. True
4. True
5. True

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5. Short Answer

1. Motion is when an object changes its position with time.
2. Linear – train on track; Rotational – fan blades; Oscillatory – pendulum.
3. To measure small lengths like pencil, book, or table.
4. Speed = Distance ÷ Time; e.g., 60 km in 2 hours = 30 km/h.
5. Uniform – moving car at constant speed; Non-uniform – speeding bicycle.

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6. Long Answer

1. Units:
   • 1 m = 100 cm
   • 1 m = 1000 mm
   • 1 km = 1000 m
2. Motion: change in position; types – linear, rotational, oscillatory
3. Speed = Distance ÷ Time; Example: Car travels 120 km in 2 h → 60 km/h
4. Instruments: Ruler (small lengths), Measuring tape (long distances), Vernier caliper (precise lengths), Stopwatch (time)
5. Uniform – constant speed; Non-uniform – changing speed

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7. HOT & Application

1. Speed = 120 ÷ 2 = 60 km/h
2. Use measuring tape or string to trace the path and then measure length.
3. Time period = Total time ÷ Number of oscillations = 40 ÷ 20 = 2 s

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8. Passage-Based

1. Change in position of an object over time.
2. Linear, Rotational, Oscillatory
3. Speed = Distance ÷ Time
4. Accurate length measurement is required to calculate speed and study motion properly.