I.3. Scalar and vectorial physical parameters

The vast majority of physical parameters can be added arithmetically, for example:

• At the market, the seller placed a watermelon on one plate and placed two marked weights on the other plate of the scale, one of 4 kg and the other of 0,5 kg, ie the melon weighs 4,5 kg.
• When you do your homework in math, you spend 1 hour and in physics 0.5 hours, a total of 1.5 hours.
• In experiment no. 1 you determined the mass, volume and density of a magnet. Apart from their numerical value and unit of measurement, can you say anything else about these three physical parameters? The answer is no.

There are cases when certain physical parameters cannot be added algebraically, for example:

• You play with a ball and throw it in different directions: up, down, obliquely. The ball moves in the direction you pushed with a certain force. In order to know everything about the force with which you act on the ball, apart from the numerical value of your force, the unit of measurement, you also have to say in which direction and in what sense you threw it.
• Two boys are pulling a car in opposite directions and, surprisingly, the car is standing still.
• If you start from point 0 and move east 6 m (A), then north 8 m (B), then west 15 m (C), you will find that at point C you are 12 m from 0 and not at 6 m + 8 m + 15 m = 29 m.

So not all physical quantities are the same, some are scalar, some are vectorial.

Scalar physical parameter (in short, scalar) is the physical parameter that is completely characterized by:

• Numeric value;
• Measurement unit.

The vast majority of physical parameters are scalar: length, area, volume, time, mass, density, temperature, current intensity, electrical voltage etc.

Vectorial physical parameter (in short, vector) is the quantity that is completely characterized by:

• Numeric value (module);
• Measurement Unit;
• Orientation:
  • Direction;
  • Sens.

To differentiate a scalar from a vector, an arrow is placed above the symbol of the vectorial physical parameter.

Examples of vectorial physical parameters:

The word scalar derives from the Latin scalaris, an adjective form of scala (Latin term meaning "ladder"). If you order several stakes according to their height, it looks like a ladder.

The word vector comes from Latin, which means carrier.

🔦 Remark

You will find out next how to work with vectors, as they add up other than scalars (the latter, having only a numerical value, without orientation, they add up like any number). Both in the curriculum and in the textbook, vector operations are mixed with different types of forces, in the next chapter no. II. I have systematized the matter differently and I will continue to give the graphical representation of a vector and the operations with vectors (for a better understanding of this topic).