Question

Why is kinetic energy scalar?

Answer 1

Hint: To answer this question first we will know what scalar quantity and vector quantity mean. Then we will know what kinetic energy is, after knowing both the terms we will make a relation to tell why kinetic energy is scalar quantity.

Complete answer:
Let us look at the definition of vector and scalar quantities:
Scalar quantities: Quantities which have only magnitude or quantities whose only size is specified are called scalar quantities.
Vector quantities: Quantities which have both magnitude and direction are called vector quantities.

Lets see what kinetic energy is; Kinetic energy is defined as energy possessed by a virtue of being in motion.it depends on mass of the object.In simple words if an object is moving it possesses kinetic energy. Examples of objects possessing kinetic energy are: ball rolling on road, a car moving down the road, river flow, etc.

Now lets build a relation to see why kinetic energy is scalar, look at the definition of kinetic energy. It tells only about energy and mass and does not mention anything about the direction in which the body/object should move. Hence we can say that kinetic energy is a scalar quantity and not a vector quantity.

Note: When we look at the formula of kinetic energy $K={\displaystyle \frac{1}{2}}m{v}^2$ we see that mass is scalar quantity whereas velocity is vector quantity. But still kinetic energy will remain a scalar quantity.do not get confused looking at the velocity being a vector quantity.