how to identify that acceleration due to gravity is positive or negative
Answers
Answer:
I would normally answer a question like this with one word when I taught physics. “Yes" This means both can be true. What matters is how you as the person trying to understand and solve the problem define what is positive or negative. So if you define towards the center of the Earth as positive then g is positive. If you define away from the center or up as positive then g is negative. If you define postive as an odd angle away from the ground instead of just up or down, like up an incline, then g could be both positive and negative.
This is why when you solve a physics problem you should always define the axis first.
If someone else has defined which way is positive then work it out.
Answer:
If the equation has a in it, like v = v0 + at, the acceleration is negative. If the equation has g in it, like W = mg, direction is implied and the acceleration is positive.
If you had a coordinate system where up is positive then gravity would be negative since its direction is the opposite of your positive direction. If you had a coordinate system where down is positive then gravity would be positive since its direction is the same as your positive direction.