Air blows from one place to another because gases move from high-pressure areas to low-pressure areas
In simple words
it happens because of pressure differences.
F=mg
if m doubled, F would double as well
Answer:
(a): 
(b): 
(c): 
Explanation:
Given that an electron revolves around the hydrogen atom in a circular orbit of radius r = 0.053 nm = 0.053
m.
Part (a):
According to Coulomb's law, the magnitude of the electrostatic force of interaction between two charged particles of charges
and
respectively is given by

where,
= Coulomb's constant = 
= distance of separation between the charges.
For the given system,
The Hydrogen atom consists of a single proton, therefore, the charge on the Hydrogen atom, 
The charge on the electron, 
These two are separated by the distance, 
Thus, the magnitude of the electrostatic force of attraction between the electron and the proton is given by

Part (b):
The gravitational force of attraction between two objects of masses
and
respectively is given by

where,
= Universal Gravitational constant = 
= distance of separation between the masses.
For the given system,
The mass of proton, 
The mass of the electron, 
Distance between the two, 
Thus, the magnitude of the gravitational force of attraction between the electron and the proton is given by

The ratio
:

Answer:
Bicycle
Explanation:
A compound machine is a machine which is a combination of simple machines.
Simple machines are like the pulley, inclined plane or a screw.
Suppose a bicycle is considered, it has more than one simple machine combined together, for it to work. Wheel and axle is one of them and the beam which is pivoted at a fixed hinge is another simple machine in it.
The pedals of the bicycle function as the lever.