Answer:
E(final)/E(initial)=2
Explanation:
Applying the law of gauss to two parallel plates with charge density equal σ:

So, if the charge is doubled the Electric field is doubled too
E(final)/E(initial)=2
21. light changes its direction when travelling through a new medium because denser mediums have a higher angle of refraction.
Answer:
The potential energy of the more massive one is twice that of the other.
Explanation:
Potential energy is given by
<em>PE</em> = <em>mgh</em>
where <em>m</em> = mass of body, <em>g</em> = acceleration of gravity and <em>h</em> = height or elevation.
For the less massive car, let the mass be
. Then its <em>PE</em> is

For the massive car, let the mass be
. Its <em>PE</em> is

But 

Hence, the potential energy of the more massive one is twice that of the other.
We can salve the problem by using the formula:

where F is the force applied, k is the spring constant and x is the stretching of the spring.
From the first situation we can calculate the spring constant, which is given by the ratio between the force applied and the stretching of the spring:

By using the value of the spring constant we calculated in the first step, we can calculate the new stretching of the spring when a force of 33 N is applied:

Answer:
The internet is most useful to them because they use it to communicate.
Explanation:
If I were to send a message to my brother in Florida, through the internet, while I'm in Pennsylvania he would get it in minutes. On the other hand if I were going to meet him and then explain what I wanted to tell him in person it would take a much longer time.