The Earth is acted upon by the gravitation of the Sun,even though it does not fall into the Sun. Why?

$A$ stone is dropped from the edge of a roof.
$(a)$ How long does it take to fall $4.9 \, m$?
$(b)$ How fast does it move at the end of that fall?
$(c)$ How fast does it move at the end of $7.9 \, m$?
$(d)$ What is its acceleration after $1 \, s$ and after $2 \, s$?

$A$ stone is dropped from the edge of a roof. It passes a window $2 \, m$ high in $0.1 \, s$. How far is the roof above the top of the window?

Two particles are placed at some distance. If the mass of each of the two particles is doubled,keeping the distance between them unchanged,the value of gravitational force between them will be

$(a)$ Name the two factors on which the buoyant force depends.
$(b)$ State the relationship between the buoyant force on an object and the weight of the liquid displaced by it.

Two stones $A$ and $B$ are dropped from a multi-storey building. Stone $A$ is dropped from $100 \, m$ and at the same time stone $B$ is dropped from $50 \, m$ height. Both of them reach the earth at the same time. Will they have equal velocity while reaching the ground? Calculate and find out the answer (Take $g = 10 \, m s^{-2}$).