Conservation of energy problem involving a projectile.

[Benzoate]

Homework Statement

An athlete putts a shot of mass 7 kg a distance of 20 m. Show that the athlete must do to
at least 700 joules of work to achieve this. (ignore the height of the athlete.)
2. Homework Equations [

E=T+V
Work=T2-T1

The Attempt at a Solution

when the ball reaches maximum height, its velocity is zero. I should problem find the angle that gives the ball its maximum range. I am not sure how to find the angle that gives the ball its maximum range. maximum range is 20 meters.

.5*m*v^2=mgz ==> v=sqrt(2gz)= 20 m/s

R cos(theta)=v*u/g

 

[Benzoate]

anyone not understand my question

 

[nasu]

I understand the question. I don't understand your solution.

The angle that gives maximum range is 45 degrees.
Use this to find the initial speed. Then find kinetic energy.

 

[borgwal]

Isn't this introductory physics?

 

[nasu]

"Isn't this introductory physics? "

It depends on the reference frame.