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

`(4)`

Explanation

Given, `h = 15m, v = 1 m/s, m = 10 kg, g = 10 ms^(-2)`
Force conservation of mechanical energy
`(PE)_(i) + (KE)_(i) = (PE)_(f) + (KE)_(f)`
` Rightarrow mgh + 1/2 mv^(2) = 0 +(KE)_(f)`
`Rightarrow (KE)_(f) = mgh + 1/2 mv^(2)`
`Rightarrow (KE)_(f) = 10 xx 10 xx 15 + 1/2 xx 10 xx(1)^(2)`
` = 150 + 5 = 155 J`