A stone is projected vertically up to reach maximum height h. The ratio of its kinetic energy to its potential energy at a heighth`4/5 h`, will be 

Options

A. `5:4`
B. `4:5`
C. `1:4 `
D. `4:1 `

Answer

C

Explanation

At a height `(4h)/5`,
Potential energy = `mg xx (4h)/(5) = 4/5 mgh`,Total energy = mgh
`:.` KE at that height = `mgh - 4/5 mgh = 1/5 mgh`
`:.` At a height `4/5 h `, the ratio of `(KE)/(PE) = (1/5 mgh)/(4/5 mgh) = 1/4`.