Hi!

Work = change in Ec

= 1/2m(v1)² - 1/2m(v2)²

= 0 - 1/2 * 0,5 * 400

= - 100J

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Hola buddy . so umm what I can see from this is that to stop the ball the goalkeeper must do negative work against it . By applying work energy theorem which is ; work done = change in kinetic energy , we can get work done by the ball on hands of goalkeeper as -100 J ( keep initial velocity 20 m/s and final velocity as 0 m/s ) . so goalkeeper’s work on the ball would be 100J .

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Thank you very much!!!

Thank you so much!!!