Question
Sat August 18, 2012 By:
 

In NCERT Textbook Class 9 (Pg.136) It Is Given That When A Body Is Travelling In Upward Direction, G=-9.8m/S2.But In NCERT Textbook Class (11 Pg 49) It Is Given That When A Body Is Thrown In Upward Direction, G=+9.8m/S2. Can You Please Explain?

Expert Reply
Sat August 18, 2012
In every case the acceleration due to gravity is same.
It always acts in downward direction. The sign depends on the direction in which this force is acting.
Suppose a body is falling then the acceleration due to gravity will aid in the motion, so we use a positive sign for it, otherwise for  a body travelling upwards, we use a negative sign as it decellerates the motion
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