physics question about gravity!!?

Question

what is the acceleration of a ball dropped? is it -9.81 or 9.81

Answer 1

all of the above answers are correct and its true that gravity's acceleration is alwayz 9.81....but i can see where u are gettin the negative from because some physics teachers teach it that way (mine did hehe) ne wayz...the whole point is that you should end up gettin a negative final velocity!!

Answer 2

I'm afraid that this is resulting in some confusion. The acceleration of gravity at the surface of the earth is always 9.8 m/sec^2 DOWNWARD - this is whether you throw a ball up, down, or sideways. If you set up your problem so that downward is negative and upward is positive (as is usually the case), then the number that you need to use in your solution to the problem is -9.8 m/sec^2.

It all has to do with initial assumptions and boundary conditions. For most problems, I think that you will be assuming UP is POSITIVE, so -9.8 m/sec^2 would be appropriate. If you are trying to find out how far an object falls when dropped from an airplane, then you might consider DOWN as POSITIVE, in which case you would use +9.8 m/sec^2. Just remember what assumption you are starting with.

Answer 3

Acceleration due to gravity is always 9.8 m/s^2

It will become negative only when:
*the object is thrown vertically upward

Moreover, 9.8m/s^2 is always constant. It only becomes negative because of the direction.

Good luck and God bless!

Answer 4

its 9.81. -9.81 is negative acceleration.