Answer:
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


Answer:

Explanation:
Given:
angular speed of rotation of friction-less platform, 
moment of inertia with extended weight, 
moment of inertia with contracted weight, 
<u>Now we use the law of conservation of angular momentum:</u>



The angular speed becomes faster as the mass is contracted radially near to the axis of rotation.
Answer:
The electron cloud
Explanation:
Metallic bonds result from interaction of positively charged metal ions with free valence electrons which now forms an electron cloud around the metal ions. Electrostatic interaction between the metal ions and the electron cloud holds the metal ions together in the metallic bond.
Answer:
V = 493421.05 [gal]
Explanation:
This is a problem that consists of handling units, we can calculate by first-hand the volume, then convert units from cubic meters to gallons.
V = 50 * 25 * 1.5
V = 1875 [m^3]
Now we need to convert units, using the proper conversion factor.
![1875[m^3]*\frac{1000lt}{1m^3} *\frac{1gal}{3.8lt} \\493421.05[gal]](https://tex.z-dn.net/?f=1875%5Bm%5E3%5D%2A%5Cfrac%7B1000lt%7D%7B1m%5E3%7D%20%2A%5Cfrac%7B1gal%7D%7B3.8lt%7D%20%5C%5C493421.05%5Bgal%5D)