A body is thrown vertically upward from a point `A` 125 m above the ground. It goes up to a maximum height of 250 m above the ground and passes through `A` on its downward journey. The velocity of the body when it is at a height of 70 m above the ground is `(g=10 m//s^(2))`

Options

A. `50 ms^(-1)`
B. `60 ms^(-1)`
C. `80 ms^(-1)`
D. `20 ms^(-1)`

Answer

B

Explanation

The initial velocity of the body
`upsilon^(2)=2 gh`
`u = sqrt(2gh)=sqrt(2xx10xx125)=sqrt(2500)=50 ms^(-1)`
The final velocity from equation of motion
`upsilon^(2)=u^(2)+2gh`
`upsilon = sqrt((50)^(2)+2xx10xx55)`
`upsilon = sqrt(2500+1100)=sqrt(3600)=60ms^(-1)`