Question

Which among the following is a vector quantity?
A) Heat
B) Angular Momentum
C) Time
D) Work

Answer 1

Hint: All physical quantities are divided into two categories: Scalar and Vector based on whether they have a direction or not. Those having direction as well as magnitude are called Vector Quantities. Those having only magnitude are called Scalar Quantities.

Complete solution:
To get the answer for this question, we will analyse all the options one by one.
Option A: Heat
Heat is a measure of hotness or coldness of a substance. As we know, hotness or coldness does not require any direction to define it. It is a measure of the current state of a body. Therefore, it is a scalar quantity. However, if we were asked about transfer of heat, it would have been a vector quantity as heat transfer always takes place in the direction of decreasing temperature.

Option B: Angular Momentum
Angular Momentum is the measure of the momentum of a body when it is in a circular motion. Like in linear motion, all bodies have momentum, while in circular motion, bodies tend to have a momentum. It is called angular momentum. Just like linear momentum, it is necessary to define a direction in which the angular momentum is acting, otherwise this quantity has no value. Therefore, Angular Momentum is a vector quantity.

Option C: Time
Time is completely separated from direction. It has no relation with direction whatsoever. Only the magnitude matters. Therefore, it is a scalar quantity.

Option D: Work
Work is the measure of the amount of work done by a body. It does not require any direction to define itself. Only its magnitude matters. Therefore, it is also a scalar quantity.

Therefore, option B is the correct option.

Note: While Scalar quantities are denoted just by a symbol, like in case of time, denoting Vector Quantities is different. Vector quantities are denoted by putting an arrow above the letter for that symbol. This arrow will indicate that the letter below it is a vector quantity.