Question

when is the acceleration takes as negative​

Answer 1

Answer:

when acceleration is opposite direction of velocity then it is taken as negative

Answer 2

Answer:

According to the principal, when an object is slowly down, the acceleration is in the opposite direction as the velocity . Thus, this object has negative acceleration.

Lets take one example - the object is moving in the negative direction (i.e.., has a negative velocity) and is speeding up.