Measurement of Length and Motion – CBSE NCERT Study Resources

We studied that a measuring tape is flexible and can measure curved surfaces, unlike a rigid meter scale.

• Place the tape along the curve, ensuring no gaps.
• Read the measurement where the tape ends.

Our textbook shows measuring a bent wire. In real life, tailors use tapes to measure cloth lengths.

A swing moves back and forth, showing periodic motion because it repeats after fixed intervals.

• The swing completes one to-and-fro movement in equal time.
• This repetition defines periodic motion.

Our textbook compares it to a pendulum clock. In parks, swings help us understand motion practically.

We use a ruler to measure straight objects like a pencil by aligning it properly.

• Place the pencil parallel to the ruler’s markings.
• Ensure one end starts at ‘0’ and read the other end.

Our textbook shows measuring classroom objects. Carpenters use rulers to cut wood accurately.

Uniform motion has constant speed, while non-uniform motion changes speed or direction.

• A car moving at 60 km/h steadily shows uniform motion.
• A bicycle slowing down near traffic is non-uniform.

Our textbook compares a fan’s blades (uniform) to a bouncing ball (non-uniform).

A stopwatch records precise time intervals, like how long a toy car takes to move.

• Start the stopwatch when the car begins moving.
• Stop it when the car stops and note the time.

Our textbook measures a ball rolling down a ramp. Coaches use stopwatches in races.

We studied that curved lines cannot be measured directly with a ruler. Instead, we use a flexible thread.

• Place the thread along the curve.
• Mark the start and end points on the thread.
• Straighten the thread and measure it with a ruler.

Our textbook shows measuring a winding river on a map. In real life, we can measure a curved road or a coiled wire.

A pendulum swings back and forth in a regular motion.

• The pendulum completes one oscillation when it returns to its starting position.
• Each oscillation takes the same time, making it useful for clocks.

Our textbook shows grandfather clocks using pendulums. In real life, playground swings also show similar motion.

Rectilinear motion is movement in a straight line.

• Objects move without changing direction.
• Speed can be constant or changing.

Our textbook shows a car moving straight on a road. In real life, a train on straight tracks also shows this motion.

We use a meter scale to measure straight objects like tables.

• Place the scale along the table's edge.
• Align the zero mark with one end.
• Read the measurement at the other end.

Our textbook shows measuring a classroom desk. In real life, we measure furniture or books the same way.

Uniform motion has constant speed, while non-uniform motion changes speed.

• Uniform: A car moving at 60 km/h steadily.
• Non-uniform: A bicycle speeding up or slowing down.

Our textbook shows a fan rotating uniformly. In real life, a bus stopping and starting shows non-uniform motion.

Measurement of length refers to determining how long or short an object is by comparing it with a standard unit, such as a meter or centimeter. For example, the length of a table can be measured using a ruler, while the height of a person can be measured using a measuring tape.

To measure a curved line (like the circumference of a circular object) using a measuring tape, follow these steps:
1. Place the starting point (zero mark) of the tape at one end of the curve.
2. Gently bend the tape along the curve without stretching it.
3. Read the measurement where the curve ends.

Two precautions for accurate measurement:

• Ensure the tape is not twisted or folded while measuring.
• Always check that the starting point is aligned correctly to avoid errors.

Additionally, using flexible tools like a measuring tape is essential for curved surfaces, as rigid rulers cannot bend to match the shape.

Motion is the change in position of an object with respect to time. For example, a moving car or a flying bird shows motion.

Uniform motion occurs when an object covers equal distances in equal time intervals (e.g., a car moving at a constant speed of 60 km/h on a straight highway).
Non-uniform motion occurs when an object covers unequal distances in equal time intervals (e.g., a bicycle slowing down while approaching a traffic signal).

A speedometer is a device in vehicles that measures and displays the speed in real-time. It works by calculating the rotation of the wheels and converting it into speed (km/h or mph). This helps drivers maintain safe speeds and avoid accidents.

Understanding these concepts helps in analyzing movement in daily life, such as tracking travel time or designing efficient transport systems.

Measurement of length refers to determining how long or short an object is by comparing it with a known quantity. For example, measuring the length of a table using a ruler or the height of a person using a measuring tape.

The importance of standard units in measurement includes:

• Ensures consistency and uniformity in measurements worldwide.
• Allows easy comparison and communication of measurements between people.

Two instruments used to measure length accurately are:

• Ruler: Used for measuring small lengths like the length of a book.
• Measuring tape: Used for measuring longer lengths like the height of a person or the length of a room.

Motion is the change in position of an object with respect to time. The different types of motion are:

• Rectilinear motion: Movement in a straight line, e.g., a car moving on a straight road.
• Circular motion: Movement along a circular path, e.g., a spinning top.
• Periodic motion: Repetitive motion, e.g., a swinging pendulum.

To measure the speed of an object, follow these steps:
1. Measure the distance traveled by the object using a ruler or measuring tape.
2. Measure the time taken to cover that distance using a stopwatch.
3. Use the formula: Speed = Distance / Time.
For example, if a bicycle covers 100 meters in 20 seconds, its speed is 5 m/s.

Understanding motion helps us predict how objects move and design better machines and vehicles.

Motion is the change in position of an object with respect to time. The different types of motion are:

• Rectilinear motion: Movement in a straight line, e.g., a car moving on a straight road.
• Circular motion: Movement along a circular path, e.g., the motion of a ceiling fan.
• Periodic motion: Motion that repeats after a fixed interval, e.g., the swinging of a pendulum.

To measure the speed of an object in motion, follow these steps:
1. Measure the distance traveled by the object using a ruler or measuring tape.
2. Measure the time taken to cover that distance using a stopwatch.
3. Use the formula: Speed = Distance / Time.
For example, if a bicycle covers 100 meters in 20 seconds, its speed is 5 m/s.

The use of standard units in measuring length is crucial for consistency and accuracy in communication and scientific work. For example, the meter is a standard unit universally accepted for measuring length. If we use non-standard units like handspan or footsteps, measurements can vary from person to person due to differences in body size, leading to confusion.

For instance, measuring a table using handspans might give different results for a child and an adult. This inconsistency can cause problems in construction, trade, and science where precise measurements are essential. Standard units ensure that everyone, regardless of location or background, understands measurements the same way.

In daily life, using non-standard units could lead to errors in buying furniture, constructing buildings, or even in simple tasks like stitching clothes. Thus, standard units like meter, centimeter, and kilometer are vital for uniformity and reliability.

Uniform motion occurs when an object travels equal distances in equal intervals of time, while non-uniform motion involves unequal distances in equal time intervals. For example:

• A car moving at a constant speed of 60 km/h on a straight highway shows uniform motion.
• A bicycle moving through traffic with varying speeds demonstrates non-uniform motion.

To measure speed in uniform motion, we use the formula:
Speed = Distance / Time.
For non-uniform motion, we calculate average speed by dividing the total distance by total time taken.

For instance, if a car travels 120 km in 2 hours, its speed is 60 km/h (uniform). If a runner covers 10 km in 1 hour but speeds up and slows down, the average speed is still 10 km/h (non-uniform). Understanding these concepts helps in analyzing movement in sports, transportation, and machinery.

The measurement of length refers to determining how long or short an object is using standard units like meters, centimeters, or kilometers. It helps us compare sizes accurately. For example, measuring the length of a table in centimeters or the height of a tree in meters.

A measuring tape is more suitable than a ruler in certain cases because:

• It can measure curved or flexible objects like a waistline or a bent pipe, while a ruler is only for straight measurements.
• It is longer (often several meters), making it ideal for measuring large distances like room dimensions.
• It is portable and can be rolled up, unlike a rigid ruler.

Thus, while rulers are great for small, straight objects, measuring tapes offer flexibility and range for varied measurements.

Uniform motion occurs when an object covers equal distances in equal time intervals, like a car moving at a steady speed of 60 km/h on a highway. Non-uniform motion involves changing speed or direction, like a bicycle slowing down near a traffic signal.

To measure the speed of an object:

• Measure the distance traveled by the object (e.g., 100 meters).
• Measure the time taken to cover that distance (e.g., 10 seconds).
• Use the formula: Speed = Distance ÷ Time.

For example, if a runner covers 50 meters in 5 seconds, their speed is 10 m/s. Speed helps us understand how fast or slow an object is moving in uniform or non-uniform motion.