Gavity, negative or positive?

Question

For gravity how do you know when to have 9.81 m/s^2 positive or negative? Thanks.

Answer 1

it depends on the direction of the motion
gravity is always downward, if ur motion is upward then it becomes negative. sign depends on the direction of the motion.

Answer 2

It depends on your frame of reference. If I throw a ball up into the air, I would say gravity is negative. However, if I were going to drop a ball from a cliff and measure the distance it fell in some amount of time, I would allow gravity to be positive.

Answer 3

negative and positive is all relative. so it depends if you are going against the force of gravity or with it. For example, to get a rocket to fly, you need force opposite direction of gravity. If you have 10m/s^2 of force and minus gravity (negative) you are left with 0.19m/s^2 of force and will start to take off very slowly.

On the other hand, if you are throwing a ball downwards, from the top of the building, you will add your force + gravity. (direction of a 2nd force relative to downward force of gravity)

Answer 4

You can have it either way. It depends on if you call 'up' positive or negative. Gravity always works downwards.

So if 'up' is positive, then gravity is negative.
But if you measure lengths downwards, then gravity is positive.

Answer 5

when the object is being thrown up it slows down(common sense)
so there is a retarding force and hence the body is decelerating and hence gravity is negative.
the same argument can used for downward motion to show gravity is positive...
hope this was helpful

Answer 6

It was fresh from memory, I just helped and looked at my son's homework problem, it was -9.81 m/s^2.
In order to remember, you just remember it was negative and the 'up' is measured positive.
Hope that it helps.

Answer 7

It's quite difficult to experience negative g. You get it in a lift, when the lift is accelerating downwards; and in an aeroplane, when you push the stick forward a bit suddenly.

Answer 8

If something moves away from earth surface, take -9.81 m/s^2 and if something moves towards earth surface, take +9.81 m/s^2.

Answer 9

if an object is moving against the forcw of gravity, i.e. moving upwards, it is negative...
on the other hand if the object is moving towwards the earth, its positive

Answer 10

is something is thrown up... then gravity slows it down, so you have a neg gravity. if something is falling down. gravity accellerates it so you have a positive gravity