Answer:
Option A
The cost of keeping the semiconductor below the critical temperature is unreasonable
Explanation:
First of all, we need to understand what superconductors are. Superconductors are special materials that conduct electrical current with almost zero resistance. This means that there is little or no need for a voltage source to be connected to them. As a matter of fact, once a superconductor is connected to a power supply, one can remove the power supply and the current will still flow.
However, most superconducts can only conduct at very low temperatures up to -200 degrees Celcius. This is because, at that temperature, their atoms and molecules are relatively settled, hence they pose little or no resistance to the flow of current.
This as you can guess is extremely difficult to do, as you will need a lot of effort to cool it to that temperature and maintain it.
This makes option a the answer:
The cost of keeping the semiconductor below the critical temperature is unreasonable.
Your answer should be D
let me know if I got it wrong
Hope this helped!
Answer:
The kinetic energy of the system after the collision is 9 J.
Explanation:
It is given that,
Mass of object 1, m₁ = 3 kg
Speed of object 1, v₁ = 2 m/s
Mass of object 2, m₂ = 6 kg
Speed of object 2, v₂ = -1 m/s (it is moving in left)
Since, the collision is elastic. The kinetic energy of the system before the collision is equal to the kinetic energy of the system after the collision. Let it is E. So,

E = 9 J
So, the kinetic energy of the system after the collision is 9 J. Hence, this is the required solution.
Answer:
A pure substance consisting only of atoms with the same number of protons in their nuclei-these appear on the periodic table
Oxygen
Hydrogen
Carbon
Sulfur
Phosphate
Nitrogen
Magnesium
Calcium
Potassium
Chlorine
(I know that these are more examples than needed, but you can use any)