Question

Answer each of the following questions in one paragraph. If you want/need, you can supplement your written explanation with diagrams or equations.

1. Provide an example of an inertial frame of reference and a non-inertial frame of reference. Explain the difference.

2. Using the Michelson-Morley experiment as an example, explain why classical mechanics was unable to explain natural phenomena.

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

Solution:

Inertia is the property of matter in which an object that is at rest wants to remain at rest, and an object that is moving wants to remain moving in a straight line unless another force acts upon it.Likewise, an inertial frame of reference is a reference frame in which an object stays either at rest or at a constant velocity unless another force acts upon it. When a body does not seem to be acting in accordance with inertia, it is in a non-inertial frame of reference or accelerating. Newton's first law states that an object at rest will remain at rest, and a body in motion will remain in motion at a constant velocity in a straight line unless acted upon by an external force. The external force in this law being a force that does not originate from the body itself. Looking at the previous definitions for inertia and an inertial frame of reference, you can see that their definitions are almost the same as Newton's first law. Another way to define an inertial frame of reference is a frame of reference in which Newton's first law remains true.Let us take an example of the bystander outside a vehicle and the traveller inside a vehicle.Now let us change the example a little bit first. Firstly, we will simplify it down to one passenger inside the vehicle. Then, let's imagine that the passenger is in a soundproof box and he or she cannot see out of it. So the traveller will have no way of knowing if it is moving or stationary. In fact, to them all that matters is that they are at rest. In our example, the bystander outside the vehicle will always be in an inertial frame of reference since he or she is at rest. For the traveller, it depends on the vehicle's movement. Let's assume the vehicle is moving in a straight line. If the vehicle is not accelerating, the passenger is in an inertial frame of reference. This is because no acceleration means the velocity is constant. If the vehicle is accelerating, the passenger is in a non-inertial frame of reference.