Conservation of energy problem involving a projectile.

1. Oct 21, 2008

Benzoate

1. The problem statement, all variables and given/known data

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. Relevant equations[

E=T+V
Work=T2-T1

3. 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

2. Oct 21, 2008

Benzoate

anyone not understand my question

3. Oct 21, 2008

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.

4. Oct 22, 2008

borgwal

Isn't this introductory physics?

5. Oct 22, 2008

nasu

"Isn't this introductory physics? "

It depends on the reference frame.