Explanation:
a) The height of the ball h with respect to the reference line is
so its initial gravitational potential energy 
is
b) To find the speed of the ball at the reference point, let's use the conservation law of energy:
We know that the initial kinetic energy 
as well as its final gravitational potential energy 
are zero so we can write the conservation law as
Note that the mass gets cancelled out and then we solve for the velocity v as
Answer:
6 m/s
Explanation:
To determine the change in speed of the object, we just need to determine its speed at t = 30 s and at t = 20 s, and then calculate the difference.
The speed at t = 30 is:
v = 6 m/s
While the speed at t = 20 s is:
u = 0
Therefore, the change in speed is:
The correct answer is B, electrons emit and absorb energy based on their position around the nucleus.
I SAID don’t copy from internet but u did
Explanation:
Regardless of the source's mobility, light travels at the same speed.
<h3>What makes special relativity so crucial?</h3>
In the calculating and interpretation of high-velocity phenomena, as well as on our methods of thinking, Einstein's special relativity has had a significant influence on the area of physics. Today, we have a considerably better knowledge of space and time than we did at the start of the century.
<h3>Why is special relativity thus named?</h3>
Because it exclusively uses inertial frames to apply the concept of relativity, the theory is known as "special". General relativity, which Einstein created, applies the principle broadly, that is, to any frame, and this theory takes the gravitational forces into account.
learn more about relativity here
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