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In this article, we will get to about various topics of Displacement. To understand unit of Displacement, you should know basic things about Displacement, its formula, and many more things. However, you will understand the following topics in the article:
Read More: Equations of Motion
What is Displacement?
The displacement is the smallest distance between the beginning and ending points. The term "displacement" refers to the measurement of a vector quantity that is different from "distance." Even though both units of direction and distance are the same, when we speak of displacement, we refer to both direction and distance, and it is defined as the smallest distance between two points on a straight line. In this article, let us learn about displacement, the S.I. unit of displacement, and other displacement units.
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Formula of Displacement
The Formula of Displacement is as follows:
Displacement = \(\bigtriangleup\)x = xf – xi
Where, \(\bigtriangleup\)x= Displacement
xf= Final position
xi = Initial position
Unit for displacement
Fundamental or base units are the units in which fundamental quantities are measured, while derived units are the units of measurement for all other physical quantities that can be generated by a sufficient multiplication or division of powers of fundamental units.
Length is one of the fundamental units which is also a unit for displacement. Now, let’s see the length in different system of units.
Read More: Angular Displacement
SI Unit of Displacement
The International System of Units, known by the abbreviation SI is the modern form of the metric system which uses metre, kilogram and second as the three basic units for measuring length, mass, and time respectively.
Displacement is denoted by metre in SI system where, one metre is the length of the path travelled by light in vacuum in 1/299,792,458 of a second (1983).
The advantages of the SI system are:
- In this system, all the derived units can be easily obtained from basic and supplementary units, which means it is a coherent system of units.
- This system makes use of only one unit for one physical quantity, which means a rational system of units.
- It is a metric system which means that multiples and submultiples can be expressed as powers of 10.
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FPS Unit of Displacement
The FPS system is the British Engineering system of units, which uses foot, pound and second as the three basic units for measuring length, mass, and time respectively. Since length’s unit is foot in FPS system, foot is also the unit for displacement in FPS system, where one foot is 12 inches and is equal to 0.3048 m.
Read More: Motion in a Straight Line
CGS Unit of displacement
The CGS system is the Gaussian system, which uses centimetre, gram and second as the three basic units for measuring length, mass, and time respectively. Since length’s unit is centimetre in CGS system, centimetre is also the unit for displacement in CGS system. (1 cm = 0.01 meter)
Other displacement units
Let's look at some more displacement units now that we've learned about the SI unit. When talking about rotational or angular displacement, some of the usual units used are degrees, revolution, radian, vibration, or cycle, in addition to the meter.
Check Important Notes for Vector Product of Two Vectors
Difference between distance and displacement
Following are some of the differences between Distance and Displacement:
| Distance | Displacement |
|---|---|
| It is the length of the path travelled by an object at a certain time. | It is the shortest distance between the initial and final positions. |
| It is a scalar quantity. | It is a vector quantity. |
| It is determined by the path taken by the object. | It is independent of the path taken by the object. |
| When distance is divided by time, we get the speed of the body. | When displacement is divided by time, we get the velocity of the body. |
| The distance cannot be zero. | Displacement may or may not be zero. |
| The distance can only have positive values. | Displacement can be positive, negative, and even zero. |
| Distance = d1 + d2 | Displacement = \(\bigtriangleup\)x = xf – xi |
Points to Remember
Following are some important points:
- Displacement is calculated as the shortest distance between starting and final point.
- Distance is a scalar quantity since it has only magnitude.
- Displacement is a vector quantity since it has both magnitude and direction.
- The FPS unit of displacement is foot.
- The CGS unit of displacement is centimetre (cm).
- The SI unit of displacement is meter (m).
- The CGS and SI are metric or decimal system of units. The fps system is not metric system.
Read More: Displacement Reaction
Sample Questions
Ques: When a man travels 10 unit from point A to B, takes a right turn and travels 6 units from there to point C, then takes left turn from there to point D. What’s the total distance travelled and magnitude of total displacement of the man?
Ans: The total distance travelled by the man =10 + 6 + 7 = 13 units.
The magnitude of total displacement of the man is the length of line AD.
AD is the hypotenuse of the right angled triangle AED. The length of AE is 3 units.The length of AD is 6 units.
AD2=DE2+AE2
AD2=62+32=36+9 =45 units
AD=45=6.7082039325 units.
However, The total distance travelled by the man =13 units.
The magnitude of total displacement of the man =6.7082039325 units.
Ques: Express 1 foot in meter, 1 cm in meter, and 1 Km in meter.
Ans: Following are the expressions:
- 1 foot= 0.3048 meter.
- 1 cm = 0.01 meter.
- 1 km = 0.001 meter.
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Ques: How many types of CGS System of Unit of Displacement are there?
Ans: There are two types of CGS System of Unit of Displacement which includes Base Units and Derived Units. Base Units includes centimeter, grams, and second, whereas Derived Units includes physical quantities such as centimeter/second.
Ques: Can the displacement be negative?
Ans: Yes, Displacement can be negative because of its vector quantity as it contains both direction as well as magnitude. It would be negitive displacement when the magnitude of the object will be same but it would travel in opposite direction.
Ques: What is the diameter of proton?
Ans: The diameter of proton in the CGS system of unit of displacement is 0.00000000000017 but in SI system of unit of displacement it is 0.000000000000000017.
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