Question

define acceleration. write its SI unit. when is the acceleration taken as negative?​

Answer 1

acceleration is change in velocity per unit time

s.i. unit is m/s^2

negative acceleration is decreasing velocity per unit time

this can also be termed as deceleration

Answer 2

Rate of change of velocity is known as acceleration

So

I unit of acceleration is m/s square

Acceleration is taken negative when body covers unequal distance in equal interval of time