Q.State Newton's law of gravitation and express it in vector form.

[!TLDR] In vector form, the force on $m_2$ due to $m_1$ is $\vec{F}_{21}=-\dfrac{Gm_1m_2}{r^2}\hat{r}_{21}$, directed back towards $m_1$. [!ANSWER] $\vec{F}_{21}= …

Newton's law of gravitation states that every particle attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them, directed along the line joining them. Writing this in vector form: if $\hat{r}_{21}$ is the unit vector pointing from $m_1$ TOWARDS $m_2$, then the force on $m_2$ due to $m_1$ is $\vec{F}_{21}=-\dfrac{Gm_1m_2}{r^2}\hat{r}_{21},$ where the NEGATIVE sign shows the force is directed OPPOSITE to $\hat{r}_{21}$, i.e. it pulls $m_2$ back TOWARDS $m_1$ (the force is attractive). By Newton's third law, the reaction f …

State the law in words, then express it in vector form using a unit vector along the line joining the two masses, with a ne …

Omitting the negative sign in the vector expression, which would incorrectly …