Answer:
Acceleration of gravity=
Explanation:
Newton's Second Law-acceleration is proportional to the net force acting on an object.
All objects usually free fall at the same acceleration of
-this regardless of their mass. This acceleration is known as acceleration of gravity.
Answer: A. Work is done on the system and heat is transferred from the system for a net decrease in internal energy.
Explanation:
A refrigerator is a device which dispenses heat from the close system to a warmer area or in the surrounding. By dispensing the heat the internal temperature of the refrigerator drops. The system of refrigerator violates the second law of thermodynamics. As it performs the work to cool the region instead of heating the region. The work is done on the system and the internal energy decreases and the heat energy is liberated to the surrounding area. A refrigerator is an open system.
Answer:
Part a)

Part b)

Explanation:
Part a)
As we know that both charge particles will exert equal and opposite force on each other
so here the force on both the charges will be equal in magnitude
so we will have

here we have

now we have

Part b)
Now for the force between two charges we can say

now we have

now we have

Darwin's atomic theory which states that atoms do not emit or absorb energy so far as they remain in allowable orbits or ground states.It also states that a spectra is produced when an electron moves to a lower energy level thereby releasing energy.