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At t = 0 a 100gm ball is thrown upwards with initial speed `v_(0) = 2` m/s in an open platform elevator which at that time is moving downward with v = 3 m/s and accelerating downward with an acceleration, `a = 3 m//s^(2)`. A drag force with magnitude `F_"DRAG"` = 0.8 N acts on the ball. Net force acting on the ball in the frame of the elevator just after it has been thrown is [`g =10 m//^(2)`] :A. 1.2 NB. 1.5 NC. 1.8 ND. 2.4 N |
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Answer» Correct Answer - B Elevator is non inertial frame of reference, therefore we must apply pseudo force. Elevator is accelerating downwards, therefore pseudo force must act upwards while mg and `F_"DRAG"` act downwards. `therefore F_"NET"` [downward] = mg -ma + `F_"DRAG"` = 0.1 × 10 – 0.1 × 3 + 0.8 = 1.5 N. |
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