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 J
C. 52.5 J
D. 155 J

Answer

D

Explanation

(d) Given, h=15 m, `v=1ms^(-1), m=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)=10xx10xx15+(1)/(2)xx10(1)^(2)`
=150+5=155J