Question four bulbs A,B,C and D are connected in a circuit shown in the figure below, the letters X, Y and Z represent three switches. Which switch is used to operate switch A separately?
Answer: x
I remember c/d. That's not a problem. But if you want 'c', you'll have to give me 'd'.
Answer: 539.4 N
Explanation:
Let's begin by explaining that Coulomb's Law establishes the following:
"The electrostatic force 
between two point charges 
and 
is proportional to the product of the charges and inversely proportional to the square of the distance 
that separates them, and has the direction of the line that joins them"
What is written above is expressed mathematically as follows:
(1)
Where:
is the electrostatic force
is the Coulomb's constant
and are the electric charges
is the separation distance between the charges
Then:
(2)
Isolating and :
(3)
Now, if we keep the same charges but we decrease the distance to 
, (1) is rewritten as:
(4)
Then, the new electrostatic force will be:
(5) As we can see, the electrostatic force is increased when we decrease the distance between the charges.
Answer:
Check the explanation
Explanation:
The escape velocity is the velocity needed by any object to overcome the gravitational force of the planet on which it’s present. Now we know that the gravitational force is directly proportional to the mass of the planet and inversely proportional to the distance of the object from the center of planet.
If we keep the mass of earth constant and decrease the size of the earth than this will decrease the distance between the object and the center of the earth and thus the gravitational force that will act on the body will increase substantially which will in turn increase the value of the escape velocity.
The value of escape velocity will keep on increasing as the size of the earth will shrink till it reaches to a point when the value of escape velocity becomes more than the speed of light and since it’s impossible to travel with a speed greater than the speed of light and therefore at this point it will become impossible for a spacecraft to escape the earth.
