can u pls help .... i dont understad when to take g positive or negetive in ques . on motion under gravity. 

Asked by Sanmit Ratnaparkhi | 3rd Sep, 2015, 09:29: PM

Expert Answer:

Acceleration due to gravity always acts in the downward direction.
 
Hence, its natural direction is downwards. However, you can consider solving any problem via two variants.
 
First variant: when object is moving upwards, take g as negative and when it is moving downwards, take g as positive. In this case distance is always taken positive.
 
Second variant: When we consider upward direction as positive and downward direction as negative, so g will always be negative. In this case distance will be either positive or negative depending on direction of motion of the object.
 
In either of the variants after calculations the answer is same.

Answered by Romal Bhansali | 4th Sep, 2015, 12:00: PM