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 die force and the ball goes upto 2 m height further, find the magnitude of the force. Consider g = 10 m/s2:

Question

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 die force and the ball goes upto 2 m height further, find the magnitude of the force. Consider g = 10 m/s2: (A) 4 N (B) 16 N (C) 20 N (D) 22 N

Tardigrade Admin · Accepted Answer

The situation is shown in figure. At initial time, the ball is at P, then under the action of a force (exerted by hand) from P to A and then from A to B let acceleration of ball during PA is a

m / s^{2}

[assumed to be constant] in upward direction and velocity of ball at A is v m/s.
Then for

P A, v^{2} = 0^{2} + 2 a \times 0.2

For AB,

0 = v^{2} - 2 \times g x^{2}

\Rightarrow v^{2} = 2 g \times 2

From above'equations,

a = 10 g = 100 m / s^{2}

Then for

P A, FB D

of ball is

F - m g = ma

[ F is the force exerted by hand on ball]

\Rightarrow F = m (g + a) = 0.2 (11 g)

= 22 N

Alternate solution :
Using work-energy theorem

W_{m g} + W_{F} = 0

\Rightarrow - m g \times 2.2 + F \times 0.2 = 0 \Rightarrow F = 22 N

Q. A ball of mass $0.2 k g$ is thrown vertically upwards by applying a force by hand. If the hand moves $0.2 m$ while applying die force and the ball goes upto $2 m$ height further, find the magnitude of the force. Consider $g = 10 m / s^{2}$ :

$4 N$

$16 N$

$20 N$

$22 N$

Q. A ball of mass 0.2kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2m while applying die force and the ball goes upto 2m height further, find the magnitude of the force. Consider g=10m/s2:

4N

16N

20N

22N

Q. A ball of mass $0.2 k g$ is thrown vertically upwards by applying a force by hand. If the hand moves $0.2 m$ while applying die force and the ball goes upto $2 m$ height further, find the magnitude of the force. Consider $g = 10 m / s^{2}$ :

$4 N$

$16 N$

$20 N$

$22 N$