Question

A stone is thrown upwards. Mention the direction of acceleration due to gravity a) When it is moving upwards. b) At the highest point of its motion. c) When it is moving downwards.

Answer 1

Answer:

moving upwards = acceleration due to gravity in downward direction

at highest point = no acceleration

moving downwards= acceleration due to gravity in downwards

Answer 2

Given:

A stone is thrown upwards.

To find:

Direction of acceleration due to gravity when:

• the stone is moving upwards

• the stone is at the highest point

• the stone is moving downwards

Solution:

Let force exerted on stone by Earth be F_(sE) ,mass of stone be m , mass of earth be M_(E).

$\therefore \: \rm{F_{sE} = \dfrac{G(M_{E})(m)}{ {r}^{2} } \: \hat{r}}$

$= > \: \rm{a_{sE} = \dfrac{ \bigg \{\dfrac{G(M_{E})(m)}{ {r}^{2} } \bigg \}}{m} \: \hat{r}}$

$= > \: \rm{a_{sE} = \dfrac{GM_{E}}{ {r}^{2} } \: \hat{r}}$

Here $\hat{r}$ denotes a direction towards the the centre of the earth.

$\boxed{= > \: \rm{a_{sE} = g = \dfrac{GM_{E}}{ {r}^{2} } \: \hat{r}}}$

So, we can see that the stone will always experience acceleration due to gravity downwards and directed towards the centre of the earth.

So, final answer is:

$\boxed{\rm{gravitational \: acc. \: directed \: downwards\: in \:all\:cases}}$