A blacksmith heats a 35 g lump of iron from room temperature until it glows (2425 degrees C) to work it. If the specific heat of
1 answer:
Answer:
37.9 kJ
Explanation:
We can calculate the thermal energy gained by the iron using the formula:
where
m = 35 g is the mass of the iron
Cs = 0.450 j/g is the iron's specific heat capacity
is the change in temperature of the iron (assuming that the room's temperature is 20 C degrees)
Substituting numbers into the formula, we find
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Answer:
811.54 W
Explanation:
Solution
Begin with the equation of the time-averaged power of a sinusoidal wave on a string:
P = μ.T².ω².v
The amplitude is given, so we need to calculate the linear mass density of the rope, the angular frequency of the wave on the rope, and the frequency of the wave on the string.
We need to calculate the linear density to find the wave speed:
μ = = 0.123Kg/3.54m
The wave speed can be found using the linear mass density and the tension of the string:
v= 22.0 ms⁻¹
v = f/λ = 22.0/6.0×10⁻⁴
= 36666.67 s⁻¹
The angular frequency can be found from the frequency:
ω= 2πf=2π(36666.67s−1) = 2.30 ×10⁻⁵s⁻¹
Calculate the time-averaged power:
P =μΤ²×ω²×ν
= ×( 0.03475kg/m)×(0.0002)²×(2.30×10⁵)² × 22.0
= 811.54 W
Answer:
ΔQ = 0.1 kJ
ΔS = -0.337 J/K
The value negative is due to the fact that there is need to be the same amount of positive change in surrounding as a result of compression.
Explanation:
GIven that:
Diameter of the piston-cylinder = 12 cm
Pressure of the piston-cylinder = 100 kPa
Temperature =24 °C
Length of the piston = 20 cm
Boundary work ΔW = 0.1 kJ
The gas is compressed and The temperature of the gas remains constant during this process.
We are to find ;
a. How much heat was transferred to/from the gas?
According to the first law of thermodynamics ;
ΔQ = ΔU + ΔW
Given that the temperature of the gas remains constant during this process; the isothermal process at this condition ΔU = 0.
Now
ΔQ = ΔU + ΔW
ΔQ = 0 + 0.1 kJ
ΔQ = 0.1 kJ
Thus; the amount of heat that was transferred to/from the gas is : 0.1 kJ
b. What is the final volume and pressure in the cylinder?
In an isothermal process;
Workdone W =
Since the gas is compressed ; then
However;
The initial volume for the cylinder is calculated as ;
Replacing over values into the above equation; we have :
The final pressure can be calculated by using :
c. Find the change in entropy of the gas. Why is this value negative if entropy always increases in actual processes?
The change in entropy of the gas is given by the formula:
where
T = 24 °C = (24+273)K
T = 297 K
ΔS = -0.337 J/K
The value negative is due to the fact that there is need to be the same amount of positive change in surrounding as a result of compression.