Motion and Measurement of Distances

Story of Transport

Early Days of Transport:

• No Transport: People walked and carried goods themselves.
• Using Animals: Later, animals helped in carrying goods and people.
• Boats:
  • Initially, boats were simple logs with hollow spaces.
  • Later, boats were made from assembled wood pieces, mimicking fish shapes.

Invention of the Wheel:

• Impact: Huge change in transportation.
• Animal-Drawn Carts: Wheels improved over thousands of years.

19th Century and Steam Engines:

• Before Steam Engines: People used animals, boats, and ships.
• Steam Engine Invention: Led to railroads and steam-driven vehicles.

Modern Developments:

• Automobiles: Cars, trucks, and buses appeared.
• Motorized Boats and Ships: Enhanced water transport.
• Aeroplanes:
  • Early 1900s: Development began.
  • Improved to carry passengers and goods.
• 20th Century Innovations:
  • Electric trains.
  • Monorails.
  • Supersonic planes.
  • Spacecraft.

How Wide is This Desk?

Importance of Measuring Distances:

• We need to know distances to decide how to travel (walk, bus, rickshaw).
• Measuring objects helps in everyday tasks.

Classroom Example:

• Paheli and Boojho share a desk and argue about space.
• They decide to measure the desk to divide it equally.

Using Gilli and Danda:

• First Attempt: Desk measured as two danda lengths and two gilli lengths.
• Second Attempt: New gilli and danda set measured differently, causing confusion.

Alternative Methods:

• Use a string marked with lengths (1/2, 1/4, 1/8) to measure the desk.
• Best solution: Use a scale from the geometry box.

Historical Measuring Methods:

• Before standard scales, different methods were used to measure distances.

Real-Life Measurement Examples:

• Tailor: Measures cloth length.
• Carpenter: Measures cupboard dimensions.
• Farmer: Measures land area for seeding and watering.

Questions about Distance:

• How tall are you?
• How long is this room?
• How wide is this desk?
• Distance from Delhi to Lucknow?
• Distance from Earth to the Moon?

Understanding Distance:

• Distance is the space between two places.
• Places can be close (ends of a table) or far apart (Jammu to Kanyakumari).

Practical Measurement:

• Let’s practice measuring distances and lengths to understand better!

Some Measurements

Understanding Measurement:

• Measurement = Comparing an unknown quantity with a known unit.
• Example: “12 foot lengths” means 12 is the number, and “foot length” is the unit.

Observations:

• Measurements using foot or handspan can differ from person to person.
• Standard units of measurement are needed to avoid confusion.

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Standard Units of Measurements

Ancient Units:

• Foot length, finger width, and step distance were common.
• Indus valley civilization had accurate measurements.
• Cubit (elbow to fingertip) used in Egypt and other places.
• Yard (distance from outstretched arm to chin) and Roman pace also used.
• In ancient India: angul (finger) and mutthi (fist).

Problems with Ancient Units:

• Different body parts vary in size, causing confusion.

Metric System:

• Created by the French in 1790 for uniformity.
• International System of Units (SI) is now used globally.
• SI Unit of Length: Metre (m).
  • 1 m = 100 cm
  • 1 cm = 10 mm
  • 1 km = 1000 m

Using Standard Units:

• Repeat measurements with standard scales.
• Learn the correct way to measure lengths and distances.

Correct Measurement of Length

Using Different Measuring Devices:

• Metre Scale: Common for measuring length.
• Tailor’s Tape: Used by tailors.
• Metre Rod: Used by cloth merchants.
• Measuring Tape: Best for measuring round objects like a tree or chest.
• 15 cm Scale: Good for small objects like a pencil.

Steps for Accurate Measurement:

1. Place the Scale Correctly:
   • Scale should be in contact with the object along its length (Fig. 7.7).
2. Handling Broken Scales:
   • If zero mark is unclear, use another mark (e.g., 1.0 cm).
   • Subtract the starting mark from the ending mark to get the length (Fig. 7.8).
3. Correct Eye Position:
   • Eye should be directly in front of the point being measured (Fig. 7.9).
   • Incorrect eye position can lead to wrong readings.

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Measuring the Length of a Curved Line

Measuring with a Thread:

Key Takeaways:

• Accuracy: Care is needed to measure distances correctly.
• Standard Units: Using standard units helps convey results accurately to others.

Moving Things Around Us

Categorizing Objects: Motion or Rest

Observation:

• Moving objects change their place (e.g., bird, ant).
• Resting objects stay in the same place (e.g., table).

Understanding Motion

• Definition: Motion is a change in the position of an object with time.
• Examples of Objects:
  • Clock: Hands move but the clock stays in place.
  • Sewing Machine: Needle moves but the machine stays in place.
  • Electric Fan: Blades move but the fan stays in place.
• Comparison:
  • Ant or train moves from one place to another.
  • Blades of a fan or hands of a clock move in a fixed pattern.

Conclusion

• Objects can be in motion or at rest.
• Motion involves changing position over time.
• Some objects have parts that move even if the object itself does not move from place to place.

Types of Motion

1. Rectilinear Motion

• Definition: Motion along a straight line.
• Examples:
  • Vehicle on a straight road.
  • Soldiers marching in a parade.
  • Stone falling.
  • Sprinters in a 100-metre race.

2. Circular Motion

3. Periodic Motion

• Definition: Motion that repeats after a fixed interval of time.
• Examples:
  • Branch of a tree moving to and fro.
  • Child on a swing.
  • Guitar strings.
  • Drum (tabla) membrane.
  • Needle of a sewing machine moving up and down.

Combination of Motions

• Example:
  • Ball rolling on the ground (rectilinear and rotational motion).
• Observation:
  • Ball moves forward and rotates.

Understanding Motion

• Motion: Change in the position of an object with time.
• Examples of Motion Around Us:
  • Snail moving on the ground.
  • Butterfly flitting from flower to flower.
  • River flowing.
  • Aeroplane flying.
  • Moon going around the Earth.
  • Blood flowing inside our bodies.

Key Points

• Motion can be determined by measuring distance.
• Different objects can show different types of motion.

Chapter Summary:

• Different modes of transport are used to go from one place to another.
• In ancient times, people used:
  • Length of a foot
  • Width of a finger
  • Distance of a step
• This caused confusion and led to the need for a uniform system of measurement.
• Now, we use the International System of Units (SI units).
• SI units are accepted all over the world.
• The metre is the unit of length in the SI system.
• Motion in a straight line is called rectilinear motion.
• In circular motion, an object moves so that its distance from a fixed point remains the same.
• Motion that repeats itself after some period of time is called periodic motion.

Keywords

Serial No.	Keywords	Serial No.	Keywords
1	Circular motion	6	Rectilinear motion
2	Distance	7	SI units
3	Measurement	8	Units of measurement
4	Motion
5	Periodic motion