Explain the term free fall and state the corresponding kinematical equations of motion in the usual notation .

Explanation

When a body falls in air , there are three forces acting on the body : ( 1 ) the gravitational force due to the earth , acting downward ( 2 ) the force of buoyancy ( upthrust ) due to air , acting upward ( 3 ) the force due to friction with air ( called air resistance ) , acting upward ( being always in the direction opposite to that of the velocity of the body ) . Under certain conditions , the force of buoyancy due to air and friction with air can be ignored compared to the gravitational force of the earth . In that case ( near the earth ' s surface ) the body falls with almost uniform acceleration ( g ) . Whenever a body moves under the influence of the force of gravity alone , it is said to be falling freely . Strictly speaking , this is true only if the body falls in vacuum .
The kinematical equations of motion , in the usual notation , are
`v=u +g t, s=ut+(1)/(2)g t^(2) and v^(2)=u^(2)+2gs`.
If the initial velocity (u) of the body is zero, `v=g t s=(1)/(2) g t^(2) and v^(2)=2 gs.`