All the radiation from stars is the result of nuclear fusion in their cores.
Answer:
Solar and nuclear power generate more than 99 percent of our civilization's energy. Every other important source of energy is a combination of these two. The majority of them are solar in nature. We discharge previously collected solar energy when we burn wood.
and
Nuclear energy, fossil energy (oil, coal, and natural gas), and renewable energy (wind, solar, geothermal, and hydropower) are all examples of primary energy sources.
Explanation:
Answer:
The solution and the explanation are in the Explanation section.
Explanation:
According to the diagram that is in the attached image, the EFFORT force at point A and the load is at O point. The torque due to weight is:
TA = W * (a * cosθ)
The torque due to effort at C point is:
TC = E * (b * cosθ)
The net torque is equal to 0, we have:
Tnet = 0
W * (a * cosθ) - E * (b * cosθ) = 0

From the figure, you can observe that a/b < 1, thus E < W
Answer:
The pressure must have increased in the process
Explanation:
The State Equation for gasses reads: 
where P is the gas' pressure, V its volume, n the number of moles of gas, R the gas constant and T the temperature in degrees Kelvin.
If the temperature of the gas doesn't change in the described process, the right hand side of the equation stays the same. If that is the case, given that when the Volume of the gas diminishes from 75 liters to 50 liters, then the pressure must have increased to keep that product "P * V" constant:

So the pressure must have gone up to 450 kilopascals.
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