Question

when a ball is let free fall from the top of building what is the acceleration and what is its sign​

Answer 1

Hey MATE!!

When a body falls from some height it experiences two forces. First is the gravitational force which is acting downwards and is producing gravitational acceleration (9.8m/s^2) which comes with positive sign as it is in the direction of motion .

Second is the force and acceleration (say deacceleration) by air drift which is acting up (agianst) the motion of the falling object hence it has a negative sign. In most of the cases we neglect it to calculate time, velocity,height etc, so that value comes out to be accurate.

Hope it helps

HAKUNA MATATA :))