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 = 1.5m,v = 1m//s,m = 10kg, g = 10ms^(-2)`
From conservation of mechanical energy
`(PE)_i + (KE)_ i = (PE)_f + (KE)_f`
`implies mgh +1/2 mv^2 =0 +(KE)_f`
`implies (KE)_f = mgh +1/2 mv^2`
`implies(KE)_f =10 xx10 xx1.5 +1/2 xx10 xx(1)^2`
`implies 150 + 5 = 155 J.`