When is acceleration due to gravity positive and when is it negative?

Answer 1

Acceleration due to gravity is negative when an object is moving up. Accl'n due to gravity is positive when an object is moving down (since gravity acts downwards on an object).

^Acceleration due to gravity is always negative, while the acceleration of the ball upward was positive due to what threw it, not gravity.

Answer 2

Acceleration is the change in an objects velocity. Velocity is a very important term in physics, which is often confused with speed. The primary difference between the two is that velocity implies a specific direction (for example, 50m/s is speed of an object, whereas 50m/s North/Northeast is a velocity). Acceleration is negative when the speed of an object is increasing in the opposite direction. So, if an object is starting to move west, increasing by 5m/s each second, it's acceleration could be written 5m/s2 west or -5m/s2 east. Furthermore, as previously stated, Acceleration is the change in velocity. This is to say that a decrease in velocity would also be acceleration (the word "deceleration" does not exist in physics as it does in English). So, if the object is slowing down, it will have a negative acceleration in the direction it is moving.

Answer 3

It all depends on the sign conventions you give to the upward and downward directions.

The choice is completely up to you.

-- If you call the direction toward the center of the Earth, downward into the mine, "positive",

then the acceleration of gravity is always positive.

-- If you call the direction away from the center of the Earth, upward into the sky, "positive",

then the acceleration of gravity is always negative.

Answer 4

Acceleration due to gravity is usually considered positive when an object is falling towards the Earth. It is negative when an object is moving away from the Earth, such as when it is thrown upwards.

Answer 5

Yes. In such a case it's usually called deceleration, but functionally

it's the same thing as acceleration in the opposite direction, and is

referred to as "slowing down".

Answer 6

If you define up (the direction in which height numbers increase) to be the

"positive direction", then the acceleration due to gravity is negative.

Answer 7

It is negative if the upwards direction is defined as positive. Acceleration is downward.