# Why is Kinetic Energy a scalar quantity?

• nineteen

#### nineteen

Why is Kinetic energy a scalar quantity? I read in an article, it said, when the velocity is squared, it is not a vector quantity anymore. Can someone fill in the gaps for me? I can't quite get what that article said. And I would be pleased if you provide some other examples other than kinetic energy. Thanks so much in advance guys...

Energy in general is a scalar quantity. It is how it is defined, whether kinetic or potential.

This is not an appropriate reference. In order to know what you read we need to know which article. Please provide a reference.

The inner product of any two vectors is a scalar quantity. So in particular, the inner product of a vector with itself, i.e., the square of the vector, is a scalar quantity.

nineteen
Try to think of it in these common sense terms.

Momentum, which is proportional to velocity, is a vector quantity. When two cars collide, it makes all the difference in the world if they were traveling in the same direction or in opposite directions.

Energy is proportional to the square of velocity. It takes the same energy (fuel burned) to accelerate a car from a stop to cruising speed, or to travel 100 km, regardless of whether the car is heading north, south, east or west.

nineteen
Energy in general is a scalar quantity. It is how it is defined, whether kinetic or potential.

This is not an appropriate reference. In order to know what you read we need to know which article. Please provide a reference.

The inner product of any two vectors is a scalar quantity. So in particular, the inner product of a vector with itself, i.e., the square of the vector, is a scalar quantity.

Thank you very much. I think I got what you taught. https://van.physics.illinois.edu/QA/listing.php?id=347&t=momentum-and-kinetic-energy This is the reference for that page I was talking about in the thread I started. This is kind of a Q and A article.

berkeman
Try to think of it in these common sense terms.

Momentum, which is proportional to velocity, is a vector quantity. When two cars collide, it makes all the difference in the world if they were traveling in the same direction or in opposite directions.

Energy is proportional to the square of velocity. It takes the same energy (fuel burned) to accelerate a car from a stop to cruising speed, or to travel 100 km, regardless of whether the car is heading north, south, east or west.

Explained so simply. Thank you very much friend.

anorlunda and berkeman