Motion can be defined as the change of an object’s position with respect to time. In this sense, every physical process, like a book falling off a shelf or even the water that flows through your tap, is an example of motion in action. So, motion can be slow like the movement of a sloth or fast like a waterfall. 

Did you know that the atom, which makes up all matter in this universe, is also in constant motion? Motion is thus very important in the physical world and it can be described in terms of the following:

1. Distance
2. Displacement 
3. Speed
4. Time

Can you think of the oldest means of transport that you have read about in your History lesson? Humans first designed vessels or boats that would float on water which was quickly followed by the invention of the wheel that could make movement on a cart possible. In the early 19th century, humans discovered the power of steam energy that could run entire trains and other means of transport. And you are, of course, familiar with automobiles, airplanes, etc. that are the latest means of transport. 

Humans have always been a curious race and this curiosity has led them to constantly develop and evolve various means of transport to get from one place to another. You can say that the whole idea of motion and measurement of distances germinated from here.

There are many moving things around us that help in understanding the concept of motion and measurement of distances better. Again, there are different ways, angles in which these objects move – curved or linear. Depending on the nature of movement, motion may be classified into three types:

1. Linear Motion
   When the particles in motion move either in a straight line or follow a curved path, it is called linear motion. This is further divided into two types:
   I. Rectilinear Motion or the movement of particles in a straight line.
   II. Curvilinear Motion or the movement of particles in a curved path.
2. Rotatory Motion
   You must be familiar with the rotation of the earth around its own axis? That is a perfect example of rotatory motion which occurs when a body like the earth rotates around its own axis.
3. Oscillatory Motion
   The motion of a body about its mean position is referred to as oscillatory motion. To understand better, imagine yourself on a swing with your friend pushing from the back. How do you feel? Don’t you feel like you are going back and forth in no particular direction but around a fixed center? That is oscillatory motion.

If you go back to the history of motion and measurement of distances, you will find various types of measurement tools and standards being used by people to make transactions, calculations, etc. Needless to say it created a lot of confusion and led scientists and mathematicians to come to an agreement to use some common standard units of measurements. In this regard, the S.I or International Standard Unit of Measurement was devised as a convention for measurement across the world. 

If you have come across terms like meter and kilometer, then you are already familiar with the S.I. system. To jog your memory,

1 meter = 100 centimeter

1 kilometer = 1000 meter

You can use a simple 4-step process to ensure correct measurement of length.

Step 1: Make sure your scale is in contact with the object that you wish to measure. 

Step 2: The scale must not be broken in order to avoid zero error, in which case a different mark should be used. 

Step 3: You can obtain the correct reading by subtracting the value from the full mark that is considered as zero.

Step 4: Avoid parallax error by placing your eye directly above the point of measurement. 

So, next time you go to school, try looking at your desk and calculating how wide is this desk using the 4-step process.

You cannot use the S.I. system while measuring the length of a curved line. You can, however, use a simple daily object like a string or thread to do so. Just tie a knot at one end of the string and keeping that at a starting point A, trace the curved line back to A. In the next step, you can simply stretch the string and gain a correct measurement of length using a standard scale. Alternatively, you can use a measuring tape to measure the curved line.

• What is motion and measurement?

Motion is the change of position of any object in relation with time, and you can obtain a measurement of this change using a standard unit. 

• What is motion in science for Class 6?

When an object changes position with respect to time, it is said to be in motion.

• What do you mean by measurement for Class 6?

Measurement gives you a sense of how far or how long or big an object is.

• What are the 7 types of motion?

The 7 types of motion are:

1. Rectilinear Motion
2. Curvilinear Motion
3. Oscillatory Motion
4. Circular Motion
5. Periodic Motion
6. Rotatory Motion
7. Linear Motion

• What is the SI unit of meters?

The S.I. unit of meter is a measure of length which is equally divided into 100 centimeters.

• What is unit in Physics Class 6?

The International Standard of Units or S.I. unit is the conventional unit of measurement of distances around the world.