`Mr. X` of mass `80 kg` enters a lift and select the floor he wants .The lift now acceleration upwards at `2 ms^(-2)` for `2 s` and then moves with constant velocity .As the lift approaches his floor ,it decelerates at the same rate as it previously accelerates .If the lift cabes can safely withstant a tension of `2 xx 10^(4) N` and the lift itself has a mass of `500 kg` ,how many `Mr.X' s` could it safely carry at one time?

Options

A. `22`
B. `14`
C. `18`
D. `12`

Answer

B

Explanation

`T - (nm + M) g = (nm + M) a`
`:. n (mg + ma) = T - Mg - Ma`

or `n = (T - M (g + a))/(m (g + a))`
`n_(max) = (T_(max) - M (g + a))/(m (g + a))`
`= (2 xx 10^(4) - 500 (10 + 2))/(80 (10 + 2))`
`= 14.58`
But answer will be `14`.