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If the net work done by external force on a partical is zero which is the following statement about the partical must be true?A. Its velocity is constantB. Its velocity is decreasedC. Its velocity is unchangedD. Its speed is unchanged |
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Answer» Correct Answer - D The work - energy theorm states that `W_("net") = Delta K = K_(f) - K_(i)` Thus `W_("net") = 0` then `K_(f) - K_(i) or (1)/(2) mv_(f)^(2) - (1)/(2) mv_(i)^(2)`, which leads to the conclusion that the speed is unchanged `(v_(f) - v_(i))`. The velocity of the partical involves both magnitude (speed) and direction. The work energy theorem shows that the magnitude or speed is unchanged when `W_("net") = 0` but makes no statement about the direction of the velocity. |
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