A ball is thrown in vertically upward direction. It returns back to the same position in 2s. Then the maximum height achieved by the ball is ...... (Take g = 9.8 `ms^(-2)`)

Options

A. `9.8m `
B. `14.7m`
C. `4.9m`
D. `19.6`m

Answer

C

Explanation

To reach at maximum height a ball need t=1 s even at that position v =0.
From `v = v _(0) - g t, , v _(0) =g t`
Now, suppose maximum height is h.
`therefore v ^(2) - v _(0) ^(2) = 2gh`
` therefore (0)^(2) - (g t) ^(2) = 2gh`
`therefore h = ((g t ) ^(2))/( 2g ) = (g t ^(2))/( 2) = ( 9.8 xx (1)^(2))/( 2) = 4.9 m`