**Acceleration** is a vector quantity defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.

If the velocity is changing by a constant amount every second it is called **constant acceleration**.

**Velocity** is a vector quantity defined as the rate at which the position of an object changes.

Traveling at a **constant velocity** means you're traveling at the same speed, in the same direction continuously. Having a constant velocity means you have zero acceleration.

Image retrieved from https://www.youtube.com/watch?v=J6EMIHTr3uE on May 29, 2019

Scalar versus Vector Quantities

Scalar quantities are described by a magnitude (numerical value) alone

Vector quantities are described by both magnitude and direction

Distance versus Displacement

**Distance:** the measurement of how far apart objects are [scalar quantity]

**Displacement:** a measurement of the change in position of a moving body. A straight line connecting the start and the end points is specified in terms of length and direction. [vector quantity]

Speed versus Velocity

**Speed:** the rate of change of distance [scalar quantity]

**Velocity**: rate at which the position changes [vector quantity]

Formula for Calculating Velocity

**There are 7 base SI units:**

- Length - metre (m)
- Time - second (s)
- Amount of substance - mole (mole)
- Electric current - ampere (A)
- Temperature - kelvin (K)
- Luminous intensity - candela (cd)
- Mass - kilogram (kg)

Some common **mathematical prefixes** to be familiar with are:

- nano (n) - 10^-9
- micro (µ) - 10^-6
- milli (m) - 10^-3
- kilo (k) - 10^3
- mega (M) - 10^6
- giga (G) - 10^9

**Scientific notation** is a way of writing very large or very small numbers. To write in scientific notation, a number between 1-10 is multiplied by a power of 10. For example: 650 000 000 can be written as 6.5 X 10^8 and 0.0000076 can be written as 7.6 X 10^-6. The power is simply an indicator of how many places you have moved the decimal point either to the left (+) or the right (-).