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Question
The force exerted by the floor of an elevator on the foot of a person is more than the weight of the person if the elevator is
(a) going up and slowing down
(b) going up and speeding up
(c) going down and slowing down
(d) going down and speeding up
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Solution
(b) going up and speeding up
(c) going down and slowing down
It means normal force exerted by the floor of the elevator on the person is greater that the weight of the person.
i.e. N > mg
(i) Going up and speeding up:
aeff = g + a
N = maeff = mg + ma (N > mg)
(ii) Going down and speeding up:
aeff = g – a
N = mg – ma (N < mg)
(iii) Going down and slowing down:
aeff = g – (–a) = g + a
N = mg + ma (N > mg)
(iv) Going up and slowing down:
aeff = g – a
N = mg – ma (N < mg)
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