Question

A player kicks a ball of mass 250 g placed at the centre of a field the ball leaves his foot with a speed of 8m/s. If the work done by the player on the ball is x j. Find the value of x.

Answer 1

see force is not given so first of all convert 250g into kg . next after converting u will get 1/4 as answer then remember thw formula of force i.e. f=m*a where f = force, m= mass, and a = acceleration . now this means F =1/4*10 { bcoz of gravitational force}the answer will be 5/2 i.e. 2.5 now go to the formula of work i.e. w = f*s 
now     w = 2.5* 10
            w= 25J
 

Answer 2

Hey !!
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Work done = change in Kinetic Energy

initital Kinetic Energy = 0

final Kinetic Energy =1/2×m×v^2

here m=0.25kg
v=8 m/s

so Kinetic Energy =1/2×0.25×8^2

=8 J

so work done = 8-0=8 joule
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thanks