Linear motion

When object is displacing during a time interval average velocity is described by formula





If we want to calculate instantaneous velocity at one point we must make time interval small (infinite small)





SI unit for velocity is meters/seconds (ms^-1).
In the case of linear motion and constant velocity we can write formula (1) as





where s is path traveled during time t. We also have






Acceleration is defined as rate of change of velocity








In SI units, acceleration is measured in meters/seconds² (ms-²)

Special way of motion is when a=const. in which case we have:

v=v₀+at,

s=v₀t+at²/2,

v²=2as+v₀²,

where v₀ is starting speed and path s is measured from time t=0. When object is speeding up value of a is positive and if object is slowing down value of acceleration 'a' is negative.
In free fall which is one of the important movements where a=const. acceleration is labeled as g and in numerical problems we calculate as g=9,81 ms^-2.
Displacement, velocity and acceleration are vectors which because of simplicity they were written as scalars.