Motion and Measurement of Distances
| Class | VI |
| Subject | Science |
| Chapter -7 | Motion and Measurement of Distances |
| Medium | English |
Keywords
Measurement: comparing and expressing an unknown quantity with a known quantity is called measurement.
Stationary objects: objects that do not change their position with time are called stationary objects.
Moving objects: objects that change their position with time are called moving objects.
Translatory motion: when an object moves as a whole from one place to another is called translatory motion.
Rectilinear motion: when an object moves in a straight line is called rectilinear motion.
Curvilinear motion: when an object moves in a curved path is called curvilinear motion.
Random motion: when an object follows no fixed path is called random motion.
Rotatory motion: when all points of an object move around a single fixed point is called rotatory motion.
Rolling motion: when an object is in rotatory as well as translatory motion is called rolling motion.
Periodic motion: when the motion of a body repeats itself after regular intervals of time is called periodic motion.
Oscillatory motion: to and fro motion of an object is called oscillatory motion.
Story of transport
The story of transport is very old. Earlier people travelled only on foot, on horse and camel. Then wheels were invented, which made travelling easier. Steam engines appeared trains and steamships started running, making travel fast and easy. Now we use aeroplanes, cars, and high-speed trains, which make travel even faster and more comfortable. This is all the story of transportation, in which our inventions have improved and advanced travel.
Standard Unit of Measurement:
The standard unit of measurement refers to a universally accepted unit used for measuring quantities of a particular physical quantity.
S.I. Unit
The International System of Units (SI) is the modern form of the metric system and is the most widely used system of measurement worldwide. It defines seven base units, from which all other units are derived. These base units are:
- Meter (m): for length or distance
- Kilogram (kg): for mass
- Second (s): for time
- Ampere (A): for electric current
- Kelvin (K): for temperature
- Candela (cd): for luminous intensity
- Mole (mol): for the amount of substance
The SI system provides a coherent and internationally recognized framework for measurements in science, industry, and everyday life.
Measuring the Length of a Curved Line
A curved line’s length cannot be directly measured using a meter scale. Instead, we can use a thread to measure the length of a curved line.
Correct Measurement of Length
When taking measurements of length, it’s important to pay attention to several key factors to ensure accuracy:
1. Choose the Right Tool: Use the correct measuring tool for the length you’re measuring.
2. Start from Zero: Align the starting point of the tool (zero mark) with the object’s edge.
3. Keep Still: Keep the object steady while measuring to avoid errors.
4. Be Precise: Use a tool that gives the level of detail you need for the measurement.
5. Read Carefully: Read the measurement at eye level, ensuring the markings align with the object.
6. Use Correct Units: Use the appropriate units (centimetres, meters, etc.) for your measurement.
7. Double-Check: Verify your measurement for accuracy and consistency
Moving Things Around Us
Things move all around us every day. When leaves move in the wind or birds fly in the sky, we see motion. Cars on roads, rivers flowing, and even people walking are all examples of things moving. This movement is important because it helps us understand how things work in nature and in our daily lives.
Types of motion
1. Translational Motion: This is when an object moves from one place to another without any rotation.
Examples – a car moving on a straight road or a ball rolling down a hill.
2. Rotational Motion: This occurs when an object spins or rotates around an axis. Examples – a spinning top, a rotating fan blade, or the Earth rotating on its axis.
3. Linear Motion: This refers to motion along a straight line.
Examples – a car moving along a road or a train moving along a track
4. Circular Motion: This type of motion involves an object moving in a circular path around a fixed point or axis. Examples – a planet orbiting the sun or a swing moving back and forth.
5. Periodic Motion: This is repetitive motion that follows a regular pattern, such as the swinging of a pendulum, the vibration of a guitar string, or the oscillation of a spring.
6. Oscillatory Motion: This is a type of periodic motion where an object moves back and forth around a central point or equilibrium position.
Examples – the motion of a swing, a vibrating tuning fork, or a pendulum.
NCERT Exercise
1. Give two examples each, of modes of transport used on land, water and air.
2. Fill in the blanks:
(i) One metre is ______________ cm.
(ii) Five kilometre is ______________ m.
(iii)Motion of a child on a swing is ______________.
(iv)Motion of the needle of a sewing machine is ______________.
(v) Motion of wheel of a bicycle is______________.
3. Why can a pace or a footstep not be used as a standard unit of length?
4. Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre,1 millimetre.
5. The height of a person is 1.65 m. Express it into cm and mm.
6. The distance between Radha’s home and her school is 3250 m. Express this distance into km.
7. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?
8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
9. Why would you not like to use a measuring tape made of an elastic material like rubber to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with such a tape?
10. Give two examples of periodic motion.
Excellent Notes
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