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    So basically i'm confused whether "g" (acceleration be freefall/gravity)
    is meant to be positive or negative. i know the value is 9.81 but when do i know whether to use the positive value or negative?

    For example a ball falling downwards which value would it be for the acceleration????

    help!
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    (Original post by RoadtoSuccess)
    So basically i'm confused whether "g" (acceleration be freefall/gravity)
    is meant to be positive or negative. i know the value is 9.81 but when do i know whether to use the positive value or negative?

    For example a ball falling downwards which value would it be for the acceleration????

    help!
    Acceleration due to gravity is scalar
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    (Original post by under8ed)
    Acceleration due to gravity is scalar
    why are you telling me this..... and youre incorrect acceleration is a vector quantity.
    I want to know whether 9.81 is positive or negative in the given situation.
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    It is positive failing towards Earth as it is accelerating and negative moving away from Earth as it is decelerating.
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    So if a projectile is rising so going upwards then the force of gravity is trying to pull it down constantly this means that G will be negative . When the object is falling down then gravity is acting on it by pulling it down and it will be negative.. So if you have a projectile being released when its moving upwards first away from earth the g value is negative. Then when its falling back down it is positive.

    Yes acceleration is a vector. Has a magnitude and a direction.
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    it depends on the question
    when you have objects going up and down e.g throwing a ball upwards then observing it fall, then only do you have to think about the negative
    otherwise its always 9.81 when object is falling
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    It depends on your axes when you set up the question, as long as you're consistent it's fine. If you say acceleration due to gravity is negative, then everything else that's pointing downwards should also be negative, if you say it's positive, then everything pointing downwards should be positive.

    For your ball, the velocity is pointing downwards after it's dropped, so it has the same sign as the acceleration. If the ball was thrown upwards instead, the ball's velocity would have the opposite sign to its acceleration just after it was thrown. Consistency is the most important thing, decide which direction is positive (or directions if you're not doing 1D stuff), then give the correct signs to all your values when you have to put them in equations.
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    (Original post by RoadtoSuccess)
    why are you telling me this..... and youre incorrect acceleration is a vector quantity.
    I want to know whether 9.81 is positive or negative in the given situation.
    I meant vector sorry... gravity itself is not vector but acceleration due to gravity is.
 
 
 
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