In a shot put event an athlete throws the shot put 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 shot put 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

`h = 1.5 m , v = 1 m//s , m = 10 kg`
` g = 10 ms^(-2)`
From conservation of mechanical energy ,
`U_(i) +K_(i)=U_(f) +K_(f)`
` :. Mgh +1/2mv^(2) =0+K_(f)`
` :. K_(f) =mgh + 1/2 mv^(2)`
` :. K_(f) = 10 xx10 xx1.5 +1/2 xx10xx(1)^(2)`
`= 150+ 5 = 155 J `