In a shotput event an athlete throws the shotput of mass `10 kg`with an initial speed of `1 ms^(-1)` at `45^@` from a height `1.5 m` above ground. Assuming air resistance to be negligible and acceleration due to gravity to be `10 ms^(-2)`, the kinetic energy of the shotput when it just reaches the ground will be

Options

A. `2.5 J`
B. `5.0 J`
C. `52.5 J`
D. `155.0 J`

Answer

D

Explanation

Given, `h = 1.5 m,v = 1 m//s, m = 10 kg, g = 10 ms^(-2)`
From conservation of mechanical energy.
`(PE)i+ (KE)i= (PE)f + (KE) f`
`rArr mgh +(1)/(2) mv^(2) =0 +(KE)f`
`rArr (KE)f = mgh +(1)/(2) mv^(2)`
`rArr (KE) f = 10 xx 10 xx 1.5 + (1)/(2) xx 10 xx(1)^(2) = 150+ 5 = 155 J`.