A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes upto 2 m height further, find the magnitude of the force. (Consider `g=10m//s^2`).

Options

A. `16N`
B. `20N`
C. `22N`
D. `4N`

Answer

b

Explanation

Let `upsilon` be the velocity given by hand when the ball reaches a height h
`:. (1)/(2)mu upsilon^(2) =mgh`…(i)
If `F` is the force applied by the hand then as per
question `(1)/(2) m upsilon^(2) + F xx 0.2 = mg (h +2)`
Using (i), `mgh + F xx 0.2 = mgh + mg xx 2`
`F = (mg xx 2)/(0.2) = 10 mg = 10 xx 0.2 xx 10 = 20 N` .