5 - if the velocity of the car changed ( changed the gear ) , after five seconds from being 2 m/s , to be 7 m/s , then there is an acceleration , this acceleration is the rate of change of velocity , or change in velocity per second , and is measured by : ΔV / Vt , the change in velocity = final velocity - initial velocity = 7 - 2 = 5 , and the change in time is given : 5 , so the acceleration =
a= 7 -2 / 5 = 1 , the unit is the unit of the numerator / unit of the denominator = (m/s) / s = m/s^2
6- if the acceleration is constant ( velocity is changed equally in equal periods of time ) EX : velocity changed from 2 to 7 to 12 to 17 where time changed respectively from 1 to 6 to 12 to 18, so this is called uniform acceleration , and you can predict the velocity of a body at certain instant if you are given the acceleration and the future instant.
7- If the velocity changes randomly ( changes with no pattern ) , so this is called non - uniform acceleration , and you can not predict its velocity after certain time .
8- rules : V= X / t , X = Vt , t= X / V OR V = ΔX / Δt
a = V / t , V = at , t = V / a OR a = ΔV / Δt
I hope this helped , and if you didn't get something just ask .
good luck