Vector, Scalar, Physical Quantity, Distance & Displacement

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Vector, Scalar, Physical Quantity, Distance & Displacement

Questions discussed in this video:

  • What is Quantity?
  • What is Physical Quantity?
  • What is Scalar Quantity?
  • What is Vector Quantity?
  • Difference between Scalar and Vector Quantities?
  • Difference between Distance and Displacement?
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Vector is a type of Physical Quantities, so let’s begin with Physical Quantities.

Quantity word was derived from Greek word “Quantus”, which means “how much” or “how great”. Quantity is simply the amount or the number of something. For example, if you have 10 chocolates then 10 is the quantity of that chocolate. If you have 5 kilograms of Sugar then 5 kilograms is the quantity. So, Quantity means the amount or the number of something.

Now, Physical Quantities are those quantities which can be measured and expressed physically or to be exact, mathematically or in other words, Physical quantities can be expressed by numbers. For example, the love or hatred you have in your heart for someone, can’t be expressed by numbers. You may use gestures to express that love or hatred, but you can’t express that by numbers. So, love and hatred are not Physical Quantities. On the other hand, you can express your weight and your height by numbers, so weight and height are the Physical Quantities.

So, every physical quantity has number and this number is known as the magnitude. This is an important point.

Now, apart from magnitude some physical quantities also have direction. That’s why there are two types of Physical Quantities. First is the Scalar quantity which only has magnitude and second is the Vector Quantity which has magnitude as well as direction. Let’s take an example to understand the both:

In this map, there is location A and location B. If a person wants to travel from location A to location B by a car then he can follow a path like this. This path is known as distance. But, if that person travels with a jetpack then the path will look like this. In this case, he displaced from location A to location B and this path is known as displacement.

Now, in both cases, the path he has covered can be expressed by numbers. So, both cases have magnitudes. Also, both cases have directions but in case of distance, there are multiple directions which can’t be used in our practical life. So, we can say distance only has magnitude. And in case of displacement there is only one direction that can be expressed mathematically and can be used in our practical life. That’s why distance is a scalar quantity with only magnitude and displacement is a vector quantity with magnitude as well as direction.

Scalar quantities and vector quantities both have magnitudes but it’s the direction that makes the difference