Conditions for equilibrium require that the sum of all external forces acting on the body is zero (first condition of equilibrium), and the sum of all external torques from external forces is zero (second condition of equilibrium). These two conditions must be simultaneously satisfied in equilibrium.
Answer:

Explanation:
As we know that the rate of heat transfer due to temperature difference is given by the formula

here we know that

A = 4 m x 7 m
thickness = 30 cm
temperature difference is given as

now we have


Answer:
The electric force is 
Explanation:
From the question we are told that
The Bohr radius at ground state is 
The values of the distance between the proton and an electron 
The electric force is mathematically represented as

Where n and p are charges on a single electron and on a single proton which is mathematically represented as

and k is the coulomb's constant with a value

substituting values
![F = \frac{9*10^{9} * [(1.60*10^{-19} ]^2)}{(2.63 * 0.529 * 10^{-10})^2}](https://tex.z-dn.net/?f=F%20%3D%20%20%5Cfrac%7B9%2A10%5E%7B9%7D%20%2A%20%20%5B%281.60%2A10%5E%7B-19%7D%20%5D%5E2%29%7D%7B%282.63%20%2A%200.529%20%2A%2010%5E%7B-10%7D%29%5E2%7D)
