- #1
sawer
- 65
- 2
This is the gravitational potential energy formula
$$U = -\int_\infty^r\vec{F}_\text{field}\cdot d\vec{r}$$
If r vector's direction is form infinity to r, then it means it has same direction as Gravitational Force. So cos0=1
But after multiplication there is a negative sign here: "-GMm"
$$U = -\int_\infty^r \frac{-GMm}{r^2} dr$$
Why is there a negative sign here(before GMm)? Doesn't gravitational force vector and r vector(from infinity to r) have same direction?
$$U = -\int_\infty^r\vec{F}_\text{field}\cdot d\vec{r}$$
If r vector's direction is form infinity to r, then it means it has same direction as Gravitational Force. So cos0=1
But after multiplication there is a negative sign here: "-GMm"
$$U = -\int_\infty^r \frac{-GMm}{r^2} dr$$
Why is there a negative sign here(before GMm)? Doesn't gravitational force vector and r vector(from infinity to r) have same direction?