a cricket ball of mass 200g moving with velocity of 15 m/s is brought to rest by a player in 0.05s what is the average force appiled by the player

Fine out you self hx

Use a magnet to separate iron, evaporate water, i'm not sure how to separate the other two i'm sorry but good luck

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The internal energy of the system we can term it as total potential energy and kinetic energy. energy flows out of the surrounding from the system then we can say that the internal energy of the final state is lower than its initials. the sign of  δesystem is negative.δesystem = efinal - einitial=-ve  efinal  ∠einitial.