# Thermal physics and Ideal gas law

Question 1: The figure below is a plot of Fahrenheit temperature versus Celsius temperature.

(a) Is the value of the y-intercept found by setting (Helpful Hint: The y-intercept is found by setting your x-value to 0. Look at the graph and determine what your x and y-axis represent.)

1. TF = TC

2. TC = 0 or

3. TF = 0?

(b) Compute the value of the y-intercept. (Helpful Hint: Slope is equal to Δy/Δx. Choose 2 points on the line (try the initial and terminal points since they are labled). Identify the x and y coordinates of each point and solve for the slope.)

(c) What would be the slope and y-intercept if the graph were plotted the opposite way (Celsius versus Fahrenheit)? . (Helpful Hint: Take the reciprocal of the value for the slope in part b)

Question 2:If 2.4 m3 of a gas initially at STP is compressed to 1.6 m3 and its temperature raised to 30oC, what is the final pressure? (Helpful Hint: P(f) = P(i)V(i)T(f)/T(i) (where i=initial and f=final).)

(see attached file for diagram)

Question 3: A driver releases an air bubble of volume 2.0 cm3 from a depth of 15 m below the surface of a lake, where the temperature is 7.0oC. What is the volume of the bubble when it reaches just below the surface of the lake, where the temperature is 20oC? (Helpful Hint: Find the pressure (P) at a depth of 15 m by (P = ρgh). Next, find the pressure at 0.078 m below the surface. Finally, use the equation V(f) = P(i)V(i)T(f)/[T(i)P(f)])

Question 4: A steel beam 10m long is installed in a structure at 20oC. What are the beam's changes in length at the temperature extremes of -30oC to 45oC? (Helpful Hint: ΔL =LoαΔT for both cases.)

Question 5: A circular steel plate of radius 0.10 m is cooled from 350oC to 20oC. By what percentage does the plate's area decrease? (Helpful Hint: Use the equation ΔA/Ao = (2α)ΔT (remember that Ao = πr^2). Multiply the result by 100 to get the percentage.)

Question 6: Will heat always flow from an object having more energy to one having less energy? Justify your answer as completely as possible, demonstrating understanding of both 'heat' and 'energy'.

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Question 1:

The figure below is a plot of Fahrenheit temperature versus Celsius temperature.

(a) Is the value of the y-intercept found by setting (Helpful Hint: The y-intercept is found by setting your x-value to 0. Look at the graph and determine what your x and y-axis represent.) See the attached file for the graph.

1. TF = TC

2. TC = 0 or

3. TF = 0?

Answer = 2

(b) Compute the value of the y-intercept. (Helpful Hint: Slope is equal to Δy/Δx. Choose 2 points on the line (try the initial and terminal points since they are labled). Identify the x and y coordinates of each point and solve for the slope.)

Y intercept = 32 oF (You get y intercept by setting x axis value zero., i.e.. Tc = 0)

Slope = Δy/Δx = (TF2 - TF1) / (TC2 _ TC1)= (212 - 32) / (100 - 0) = 1.8 F/C

Lets call the slope = m,

m = 1.8

The graph is of the form : y = mx +c

TF = m Tc +32 <==> y = mx +c

(c) What would be the slope and y-intercept if the graph were plotted the opposite way (Celsius versus Fahrenheit)? . (Helpful Hint: Take the reciprocal of the ...

#### Solution Summary

This solution contains detailed answers to six physics questions related to heat. Questions involve the relationship between Fahrenheit and Celsius temperatures, deformation of matter due to temperature changes and Ideal gas law. Please download this solution bundle to further your problem solving skills in thermal physics.

Thermal Physics Entropy

An ideal gas has a specific heat given by Cv = A+BT, where A and b are constants.

Show that the entropy per kilo-mole in going from state (v1,T1) to state (v2,T2) is:

delta(s) = A ln (T2/T1)+ B(T2-T1)+ R ln (v2/v1).

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