A small branch is wedged under a 200 kg rock and rests on a smaller object. The smaller object is 2.0 m from the large rock and the branch is 12.0 m long. (a) If the mass of the branch is negligible, what force must be exerted on the free end to just barely lift the rock?
(b) What is the mechanical advantage of this lever system?

a

b

Explanation:

From the question we are told that

          The mass of the rock is  

          The  length of the small object from the rock is  

          The  length of the small object from the branch

An image representing this lever set-up is shown on the first uploaded image

Here the small object acts as a fulcrum

The  force exerted by the weight of the rock is mathematically evaluated as

substituting values

 So  at  equilibrium the sum  of the moment about the fulcrum is mathematically represented as

Here   is very small so  

                               and  

Hence

=>    

substituting values

The  mechanical advantage is mathematically evaluated as

substituting values

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.