Question

define acceleration and staste its SI unit. for motion along a straight line, when do we consider the acceleration to be (i) positive (ii)negative​

Answer 1

Answer:

acceleration is change in velocity per unit time.

si uni is ms-².

Answer 2

Acceleration can be defined as the rate of change of velocity of a body. It's SI unit is m/s^2.
acceleration is considered to be positive
when it acts along the direction of motion.
When acceleration acts opposite to the direction of motion, it is considered negative.