Question

PLEASE CLEARLY ANSWER ALL 3 PARTS:

3. Using at least one of Einstein's "thought-experiments", explain how special relativity addresses how it is possible for observers in two different inertial reference frames to “disagree” about time and distance intervals.

4. Describe how special relativity explains the conditions under which classical mechanics breaks down.(When would you, as an observer begin to notice the effects of time dilation and length contraction?)

5. In the early 20th century, the law of conservation of mass was replaced by the law of conservation of mass-energy. Why was this change needed, and how does E=mc² relate to the special theory of relativity?

Answer 1

Answers-

3- The thought experiment which I am going to tell you is the experiment which Einstein told his friend Michele Besso -

Imagine you are in the middle of a train which is moving very fast than any known train and I am standing on the ground,outside the train.Now,I want you to imagine,as the train flying past, two lightning bolts crashing beyond the tracks at the same time 100 meters apart.Would the lightning bolts be simultaneous for you? The answer is my friend is NO because you were moving towards one and away from the other.To me,standing still,they were simultaneous.How could the two of us experience the same event differently? So that means time interval is different for both of us that means time is relative not absolute.

4- When the speed of the object becomes comparable to the speed of light then the law of Classical mechanics of absolute time,absolute length etc seems to be failed.

If an object(Car or Train) moves near to the speed of light then with inside that object time slows down.This is called time dilation. [T=To/(1- v^2/c^2)^0.5]

Also if the object moves near to the speed of light then its length will be contacted in the direction of motion. This is called length contraction. [L=Lo*(1- v^2/c^2)^0.5]

5-In the early 20th century,the law of conservation of mass was replaced by the law of conservation of mass-energy because Einstein told us from his mass-energy conservation equation(E=mc^2) that the mass is the direct measure of energy contained in a body, in other words "Light carries mass".So if in a case mass is not equal in a system(For example any nuclear reaction) then there must some mass converted in to the energy.So if we know the energy then we will find that how much mass was used to create this energy and thus we will find that mass is equal both the sides. So conservation of mass is an incomplete law, so if energy and mass is directly related so it should be Mass energy conservation.

I hope the above explanation will help you to find the answer of your questions.

I will recommend you to watch the National geographic channel's show Genius; Season 1 if you want to know more and more about Einstein,his idea of relativity,his struggle to build a General Theory of Relativity and many more.You will really enjoy this show I assure you.

Thank you, have a good day.