Scalar (physics) facts for kids

A scalar is a type of measurement in physics that only tells you "how much" or "how big" something is. It's a physical quantity that is described only by its size, also known as its magnitude.

Think about it like this: When you say the temperature is 20 degrees Celsius, you don't need to say "20 degrees Celsius to the north." The 20 degrees Celsius is just a size or amount, and that's all you need to know. That's what a scalar is!

What is a Scalar?

A scalar quantity is a measurement that only has a value or size. It doesn't have any direction associated with it. For example, when you measure your weight, you just say "50 kilograms." You don't say "50 kilograms upwards" or "50 kilograms to the left." The 50 kilograms is the magnitude, and that's all that matters for weight.

Scalar vs. Vector: What's the Difference?

To understand scalars even better, it helps to know about their opposite: vectors.

• A scalar only tells you the size (magnitude).
• A vector tells you both the size (magnitude) AND the direction.

Let's look at some examples:

• Speed is a scalar. If you say a car is going 60 kilometers per hour, that's its speed.
• Velocity is a vector. If you say a car is going 60 kilometers per hour to the east, that's its velocity. It includes direction.

Everyday Examples of Scalars

Many things we measure every day are scalars. Here are a few common ones:

• Temperature: How hot or cold something is. You just need the number, like 25 degrees Celsius.
• Mass: How much "stuff" is in an object. For example, a bag of sugar might have a mass of 1 kilogram.
• Time: How long something takes. You measure it in seconds, minutes, or hours.
• Distance: How far you've traveled. If you walk 5 kilometers, that's your distance.
• Volume: How much space something takes up. A bottle of water might hold 1 liter.
• Energy: The ability to do work. It's measured in joules.

These quantities are all scalars because their description is complete with just a number and a unit. You don't need to add a direction to them.

See also

• In Spanish: Escalar (física) para niños