Why is it sometimes gravity is positive 9.8 and sometimes -9.8? Like in kinematics equations, you use the negative. But in F=ma, you would use the positive.
2006-10-24 14:07:17 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Physics
acceleration due to gravity (g) is a vector with magnitude and direction. Gravity acts downwards due to earth's gravitational pull and hence is taken as positive downwards (+9.8m/s^2). If you use 'g' in formula where acceleration upwards opposing normal downward force, it is used as negative (-9.8m/s^2). simple example, throw a stone upwards and as it goes up acceleration is opposing the gravitational pull. But when it falls down, it is accelerated by gravitational pull.
2006-10-24 19:12:57 · answer #1 · answered by Jasee J 2 · 0⤊ 1⤋
gravity is a force so it should be a vector. Vector include magnitude and direction; but in F=ma force is measured in its own unit N (newton), and since the object is being accelerated the force should be always positive.
2006-10-24 15:52:14 · answer #2 · answered by Anonymous · 0⤊ 1⤋
When setting up a formula involving g. You have to choose one direction as positive. If you choose up as positive anything pointing down (like g) will be negative.
2006-10-24 14:10:09 · answer #3 · answered by Benny B 2 · 4⤊ 0⤋
Hi. A body that is not being held somehow will FALL at the rate of 'g' (positive). A body being held is subject to a FORCE of 'g' (negative)
2006-10-24 14:10:36 · answer #4 · answered by Cirric 7 · 2⤊ 0⤋
But sometimes in certain problems we take uboth up and downward gravity as - ve
Why??????
2015-07-17 17:14:41 · answer #5 · answered by JI 1 · 0⤊ 0⤋