Answer:
B.convection currents in the mantle
Explanation:
The density of sample is 5 g/cm3
Given:
volume of sample = 20 cm3
mass of sample = 100 grams
To Find:
density of sample
Solution: Density is the measure of how much “stuff” is in a given amount of space. For example, a block of the heavier element lead (Pb) will be denser than the softer, lighter element gold (Au). A block of Styrofoam is less dense than a brick. It is defined as mass per unit volume
density = mass/volume
d = 100/20
d = 5 g/cm3
So, density of sample is 5 g/cm3
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To solve this problem we will apply the concepts related to the final volume of a body after undergoing a thermal expansion. To determine the temperature, we will use the given relationship as well as the theoretical value of the volumetric coefficient of thermal expansion of copper. This is, for example to the initial volume defined as 
, the relation with the final volume as
Initial temperature = 
Let T be the temperature after expanding by the formula of volume expansion
we have,
Where 
is the volume coefficient of copper 
Therefore the temperature is 53.06°C
Answer:
the claim is not valid or reasonable.
Explanation:
In order to test the claim we will find the maximum and actual efficiencies. maximum efficiency of a heat engine can be found as:
η(max) = 1 - T₁/T₂
where,
η(max) = maximum efficiency = ?
T₁ = Sink Temperature = 300 K
T₂ = Source Temperature = 400 K
Therefore,
η(max) = 1 - 300 K/400 K
η(max) = 0.25 = 25%
Now, we calculate the actual frequency of the engine:
η = W/Q
where,
W = Net Work = 250 KJ
Q = Heat Received = 750 KJ
Therefore,
η = 250 KJ/750 KJ
η = 0.333 = 33.3 %
η > η(max)
The actual efficiency of a heat engine can never be greater than its Carnot efficiency or the maximum efficiency.
<u>Therefore, the claim is not valid or reasonable.</u>
