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Unformatted text preview: a) What is the acceleration of the block? Is it speeding up or slowing down? Two forces are exerted on the block: the normal force from the floor and the gravitational force. Taking upward as positive, we apply Newton’s 2 nd to the block. ma = F N – mg ⇒ a = (F N – mg)/m = -0.800 m/s Since the elevator is moving upward, the negative acceleration means it is slowing down. b) How much work is done on the cab by the force from the cable? Three forces are exerted on the elevator: the tension force, the gravitational force and downward force F N from the block. Newton’s 2 nd law yields Ma = T – Mg - F N T = M(g+a) + F N = 8100 N The work done by the tension is W T = Td = 20250 J...
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- Spring '08
- Force, constant magnitude FN, Tomoyuki Nakayama