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.
The gravitational force between Mars and the Sun is 
Explanation:
The magnitude of the gravitational force between two objects is given by the equation:
where
is the gravitational constant
m1, m2 are the masses of the two objects
r is the separation between them
In this problem, we have:
is the mass of the Sun
is the mass of Mars
is the average distance Mars-Sun
Substituting into the equation, we find the gravitational force:

So, the closest answer is

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Answer:
The angular speed is 
Explanation:
From the question we are told that
The time taken is 
The number of somersaults is n = 1.5
The total angular displacement during the somersault is mathematically represented as

substituting values


The angular speed is mathematically represented as

substituting values


Answer:
The speed of meteoroid is 21.61 km/s in south-east.
Explanation:
Given that,
A meteoroid is traveling through the atmosphere at 18.3 km/s. while descending at a rate of 11.5 km/s it means 11.5 km/s in south.
We need to draw a diagram
Using Pythagorean theorem




Hence, The speed of meteoroid is 21.61 km/s in south-east.
amount of work done is 5880 J
Given:
mass of object = 50kg
Final height = 20m
initial height = 8m
To Find:
amount of work done
Solution:
work is done when a force acts upon an object to cause a displacement. You can calculate the energy transferred, or work done, by multiplying the force by the distance moved in the direction of the force.
The work done by gravity is given by the formula,
W = mgh
W = 50 x 9.8 x ( 20-8)
= 5880 J
So the work done is 5880 J
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