Question

17. A stationary football is kicked by a player suchthat it attains a speed of 3 m/s just after the kick.Find the work done by the player on the ball if themass of the ball is 100 g.​

Answer 1

$\huge{\bold{\underline{\underline{....Answer....}}}}$

$\huge{\bold{\underline{Given:-}}}$

Initial velocity (u) = 3 m/s.

Final velocity (v) = 0 m/s.

(As at highest point of its journey the velocity will be Zero.)

a = - g = - 10 m/s².

(The ball is travelling against gravity)

$\huge{\bold{\underline{Explanation:-}}}$

Firstly finding the Height attained by the body,

From third kinematic equation,

$\large{\bold{v^2 - u^2 = 2as}}$

Substituting the values,

$\large{(0)^2 - (3)^2 = 2 \times- 10 \times H}$

$\large{0 - 9 = - 20 \times H}$

$\large{- 9 = - 20 \times H}$

$\large{ \cancel{-} 9 = \cancel{-} 20 \times H}$

$\large{9 = 20 \times H}$

$\large{H = \frac{9}{20}}$

$\large{\boxed{H = 0.45 \: m}}$

Now, Work done

$\large{\bold{W = mgh}}$

Substituting the values,

$\large{W = 0.1 \times 10 \times 0.45}$

As Mass is given in grams we need to convert it in to Kg.

So, 100 grams = 0.1 Kg.

Now,

$\large{W = 1 \times 0.45}$

$\huge{\boxed{\boxed{W = 0.45 \: J}}}$

So,the work done by the player is 0.45J.