- #1
oneplusone
- 127
- 2
I don't get the difference between these equations:
[itex] U = \dfrac{-Gm_1m_2}{r} [/itex]
[itex] F_g = \dfrac{-Gm_1m_2}{r^2} [/itex]
[itex] g = \dfrac{F_g}{m} = \dfrac{GM}{r^2} [/itex]Also, why are the first two negative?
Here's my thinking:
The first equation is like U=mgh. Except it's when two masses are very far apart. It is used when you are dealing with conservation of energy.
The second equation looks like a force, but I can never tell how it's acting. For example, consider the Earth and the sun. They both have a gravitational force on each other, which are equal and opposite. So is the net force zero?? But then why can the Earth orbit around the sun? ANd why is the equation negative?
The third equation, i have no clue about.
Please help! very confused!
Cheers.
[itex] U = \dfrac{-Gm_1m_2}{r} [/itex]
[itex] F_g = \dfrac{-Gm_1m_2}{r^2} [/itex]
[itex] g = \dfrac{F_g}{m} = \dfrac{GM}{r^2} [/itex]Also, why are the first two negative?
Here's my thinking:
The first equation is like U=mgh. Except it's when two masses are very far apart. It is used when you are dealing with conservation of energy.
The second equation looks like a force, but I can never tell how it's acting. For example, consider the Earth and the sun. They both have a gravitational force on each other, which are equal and opposite. So is the net force zero?? But then why can the Earth orbit around the sun? ANd why is the equation negative?
The third equation, i have no clue about.
Please help! very confused!
Cheers.