Using the standard convention "positive is up", what is the sign of the acceleration of a rock you throw up (a) as it is going up, and (b) as it is coming back down?

(a) Negative

(b) Positive

Explanation:

Here is a question on sign.

(a) When the rock is going up, it is working against gravity. In this case, the acceleration due to gravity will take a negative value. This is because gravity works or acts downwards

(b) When the rock is coming down, it is actually working with gravity. So in this case, the sign will ne positive

where is the