Question

You like to swim at a nearby lake. On one side of the lake is a cliff, and the top of the cliff is 69 m above the surface of the lake. You dive of the cliff doing somersaults so as to have an angular speed of 5.5 rev/s. How many revolutions do you make before you hit the water? Assume your initial centre of mass velocity is horizontal and you begin from a standing position.

Answer 1

so, the only thing to calculate is the time to fall.

Multiply that by 5.5 to get the revs.

Hmmm. How about the old s = 1/2 at^2

Sloppy language. The center of mass is a point, and cannot be horizontal. Assume the velocity is horizontal, so there is no initial vertical component.

And watch out for those rocks at the bottom of the cliff!!! That's where the horizontal velocity comes in. :-)

And, the water better be shallow. At 5.5rev/s you'll be too dizzy to swim when you hit!