 In this video, we will answer the question is gravity positive or negative in free fall and gravity here is acceleration due to gravity. Alright, so before we answer this, let's first understand what free fall really is. So free fall, we can define free fall as this is this is any motion of a body where gravity is the only force acting upon it. So this would include cases when let's say when someone is dropping a ball from a height and the ball starts falling down, then the only force acting on the ball really is just the force of gravity. And because of that force, there is an acceleration which the ball is experiencing and that is called acceleration due to gravity. Also, also if someone throws a ball up and then the ball comes down, the moment the ball leaves the person's hand from that moment onwards, there is only one force acting on the ball and that is the force of gravity. And throughout the entire journey of the ball in this case, the force of gravity is acting downwards all throughout. And because the force is acting downwards, there is an acceleration due to that gravity which is constantly acting downwards throughout the journey of the ball from when the ball left the hand till the ball reaches the ground. And one might think if you look at this motion closely, one might think that when the ball is going up, we can see that the speed really is decreasing and after the ball crosses the highest point then the speed increases. So one might think that gravity, the acceleration due to gravity might be negative in the beginning because the speed is decreasing and it might be positive when the ball crosses the highest point after that because the speed is increasing. So one might think that the sign of gravity might change, might change in two parts of this motion but that is actually not true, that is wrong because the sign of gravity, the sign of acceleration due to gravity only depends on which direction you take as positive and which direction you take as negative. So if we remove this one, if you focus on this case and for this case, let's say the top direction, let's say if we take the top direction as the positive direction, this is the positive direction. So now when the ball is falling down and because the ball is released, it is dropped so the initial velocity is just zero. As the ball falls down, its velocity is in the downward direction and acceleration is also in the downward direction. So acceleration also is, it's the same value constant throughout and it's in the downward direction. And we can see that the acceleration is not in the positive direction. So acceleration here, we will take A as minus G and that is minus 9.81 meters per second squared. So if we try and tell where the ball is, let's say after time two seconds, it's a random time, let's say after time two seconds, we can use a kinematic equation which will tell us the displacement of the ball after two seconds. So we know that initial velocity is zero. We can use this equation and here we will see that this factor right here, ut, this is just zero. A here is minus 9.81 and t is, we took t as two seconds, so that would be half into, I'm just taking this as 10 just for the sake of simple calculation. And because the acceleration is downwards, positive direction we took as upwards, this is minus 10 into 4. So this really is minus 20 meters. Now what this tells us, what this minus sign tells us is that the displacement is in the negative direction and it's the magnitude is 20 meters, but there's a minus sign which means it's in the negative direction. And that makes sense because the positive direction is upwards, it's not downwards. But if we took the downward direction as positive, let's see what we get then. If this direction is positive, let's do a similar calculation. So we are interested in figuring out the displacement after two seconds, that would be s is equal to ut plus half 80 square. But now the acceleration really, this is plus 10, acceleration would be plus 10 meters per second square because acceleration is in the positive direction. So ut here is zero, this is again zero. And half 80 square, this would be half into 10 into 4. And this will come out to be equal to 20, 20 meters. Again the magnitude is the same, but now we do not have any negative sign because we took the downward direction as positive and the ball is displacing downwards. So it makes sense that we do not get a negative sign. So really all it depends on which direction you take as positive and which direction you take as negative. So is gravity positive, negative and free fall? Well, it depends on whether the acceleration is in the same direction as the direction that you chose positive. Then acceleration is positive. If the acceleration to gravity is in the opposite direction to the direction that you took as positive, then the acceleration to gravity will be negative. So it really depends on the direction you take as positive and the direction you take as negative and how the acceleration to gravity is oriented relative to that.