A particle is projected upwards with velocity v = 30 m/s. There are two points A and B at height `h_(A) = 25 m` and `h_(B) = 40 m`. If the particle crosses point B twice in a time interval `DeltaL`. Then, it will also cross A twice in a time interval equal to

Options

A. `2 Delta t`
B. `1.5 Delta t`
C. `3 Delta t`
D. `2.5 Delta t`

Answer

A

Explanation

`h_("max") = (u^(2))/(2g) = 45 m`
Time to go the C to B,
`5 = (1)/(2) g t^(2)`
`t = 1s, " So " Delta t = 2s`
Time to go from C to A,
`20 = (1)/(2) g t^(2)`
`t = 2s`
`Delta t_(A) = 2 xx 2 = 4s = 2 Delta t`