Answer:
1. Recollapsing universe
2. Critical universe
3. Coasting universe
Explanation:
Recollapsing universe has dark matter density greater than critical density. While critical universe has its matter density equal to the critical sensity. Coasting universe on the other hand has much smaller matter density compared to critical density.
Note that the critical density is approximately 10^-20 grams/cm3
Answer: 2025mm²
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The effective temperature of a star is relative to the
fourth root of the luminosity and is contrariwise proportional to the square
root of the radius.
L = k R² T⁴
If the radius remains continuous, while the luminosity doubles, the temperature
must increase by a factor of the fourth root of two.
If L → 2L, then T → 1.189207115 T
So the answer is approximately 1.19 times.
The population comes to be dominated by smaller, slower-growing individuals
Answer:
The error he made was that he didn't convert the unit of temperature to Kelvin.
The correct efficiency is 24%
Explanation:
Parameters given:
Temperature of hot reservoir = 100°C = 373 K
Temperature of cold reservoir = 10°C = 273 K
The efficiency of a heat engine is given as:
E = 1 - (Qc/Qh) = 1 - (Tc/Th)
Where
Qc = Output heat;
Qh = Input heat;
Tc = Temperature of the cold reservoir;
Th = Temperature of the hot reservoir.
=> E = 1 - (283/373)
E = 1 - 0.76
E = 0.24
In percentage,
E = 0.24 * 100 = 24%
Hence, the efficiency of the engine is actually 24%.
The error he made was that he didn't convert the temperature to Kelvin. If we leave the temperatures in °C, we have that:
E = 1 - (10/100)
E = 1 - 0.1 = 0.9
In percentage,
E = 0.9 * 100 = 90%
