Why is potential energy negative? What does that even mean?
This is really just a definition! When we ask what the potential energy of an object is, we are really asking what energy is available to be extracted. In the case of gravity: two objects separated by an infinite distance are DEFINED to have zero gravitational potential energy. As they fall together their potential energy becomes more negative, and because of the conservation of energy their kinetic energy increases so that the total energy remains zero.
The minus sign in the gravitational potential energy is really just a convention we use to keep track of energy - there is no physical meaning behind it. We could equally define it the other way round so that kinetic energy was negative!
BT
Related Physics A Level answers
All answers ▸If the highest frequency a song is 10 kHz and it is encoded at 16 bits per sample what is the minimum number of bytes needed to encode the 3 minute song?
Using the substitution u=cosx + 1, show that the integral of sinx e^cosx+1 is equal to e(e-1), for the values of x between x=π/2 and x=0
How does light from distant stars show how fast they are moving away from us.
Explain Newton’s law of Gravitation