The deceleration experienced by the gymnast is the 9 times of the acceleration due to gravity.
Now from Newton`s first law, the net force on gymnast,

Here, W is the weight of the gymnast and a is the acceleration experienced by the gymnast (
acceleration due to gravity)
Therefore,
OR 
Given
and
Substituting these values in above formula and calculate the force exerted by the gymnast,


It's called a star when it creates its own energy
Mar 28, 2011 · The Hoover Dam generates
electricity using hydropower. Hydropower is the power generated by
moving water. Dams are often built on a large river, so the water falls
down from the top of the dam. At the bottom of the dam, the water
rotates a large turbine
Hope this helps :p