An elecator in which a man is standing is moving upwards with a speed of `10ms^(-1)` if the man drops a coin from a height of 2.45 m from the floor of elevator it reaches the floor of the elevator after time `(g=9.8ms^(-2))`

Options

A. `sqrt(2)s`
B. `1//sqrt(2)s`
C. `2s`
D. `1//2s`

Answer

B

Explanation

Let the initial relative velocity relative acceleration and relative displacement of the with respect to the floor of the lift be `u_(r),a_(r)` and `s_(r)`
then `s_(r)=u_(r)t+(1//2)a_(r)t^(2)`
and `u_(t)=u_(c)-u_(l)=10-10=0`
`a_(r)=a_(c)-a_(l)=(-9.8)-0=-9.8ms^(-2)`
`s_(r)=s_(c)-s_(l)=-2.45m`
`-2.45=0(t)+(1//2)(-9.8)t^(2)`
or `t^(2)=(1)/(2)ort=(1)/(sqrt(2))sec`