A body of mass 5 kg is thrown vertically up with a kinetic energy of 490 J.The height at which the kinetic energy of the body becomes half of the origibnal value is

Options

A. 5m
B. 2.5 m
C. 10m
D. 12.5 m

Answer

A

Explanation

Let at height h the kinetic energy of the body becomes half of the original value.
According to low of conservation of mechanical energy,
`(1)/(2)mu^(2)=(1)/(2)((1)/(2)mu^(2))+mgh`
490=295+5`xx9.8xxh`
`h=(245)/(5xx9.8)=5m`