vectors and scalars
What makes a number useful ? Its Units !!!
Units are not all the same, as the quantities they measure are also as different.
A Scalar quantity is one that relates to us how big (or small) a value is. We are very used to such values and these are operated on by the usual methods.
A Vector is a quantity that also specifies a direction as well as the size of the value.
quantity = number
A quantity is something we can measure and can give this thing we measure a value. All values need to have units attached as to make sense for communication.
a Scalar quantity is a value that can change and has units it can be measured in but it has no need for direction in its value.
Mass is defined as a the amount of matter in a body.
This can also only be a positive value as you cannot have negative matter!
Mass also has no relationship with direction.
The matter is in the body at all times and does not move, so for mass we have no need for direction to define the quantity.
Therefore mass, as a general count of the number of minuscule particles in a body, is a Scalar Quantity.
Usually measured in grams or kilograms, but older people may use outdated units the pound (lb), ounce (oz) or stone
Money, you earn money your amount of money goes up, somebody elses goes down.
You spend money your money goes down as someone elses increases, money only gets added or subtracted
Lets think about time for a moment.
Time goes forward no matter what we do, we count it on a clock and on a calender. The value of time gets bigger at the same rate.
Time has no need for other direction, thus time is a scalar quanity.
now lets think about Speed.
take out the toy cars
Imagine 2 cars 1km apart, both are travelling at 100km/h along a small lane. What will happen them ?
There is more than one outcome!
Why is more than one outcome?