The force exerted by the floor of an elevator on the foot of a person standing there is more than the weight of the person if the elevator is

Options

A. going up and slowing down
B. going up and speeding up
C. going down and slowing down
D. going down and speeding up

Answer

b,c

Explanation

If elevator is slowing down acceleration `= -a`
If elevator is speeding up acceleration `=+a`
going up and slowing down
`R - mg = m (-a)`
`R = m (g -a)`
(b) going up and speeding up
`:. R - mg = ma R = m (g + a)`
(c) going down and slowing down
`mg - R = m (-a)` or `R = m (g + a)`
(d) going down and speeding up
`mg - R = ma` or `R = m (g -a)` .