WCCC 4

#wccc#physics#thermodynamics

Info

Use the following information to answer questions 9-11.

A physics teacher is holding a hot cup of coffee in her hand as she marks exams. She is so busy marking the exams that she forgets to drink the coffee and, eventually, the cup of coffee reaches thermal equilibrium with her hand.

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Question 9 What is temperature a measure of?

1. how hot each particle in a system is
2. the total kinetic energy of a system
3. the internal energy of a system
4. the average translational kinetic energy of the particles in a system

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Question 10 What does it mean for the teacher’s hand to be in thermal equilibrium with the cup of coffee?

1. There is no force between the hand and the cup of coffee.
2. The hand and the cup of coffee are at the same temperature.
3. The particles in the hand and the cup of coffee have stopped moving.
4. The temperatures of the hand and the cup of coffee add to zero.

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Question 11 Describe how the average translational kinetic energy of the particles in the teacher’s hand compares with the average translational kinetic energy of the particles in the cup of coffee throughout the process of reaching thermal equilibrium.

At the start, the average translation kinetic energy (i.e. temperate) of the teacher’s hand would be lower than that of the coffee, because the coffee’s kinetic energy means that the particles move much more than that of the hand. Throughout the process of reaching thermal equilibrium, the faster moving particles in the coffee collide with the slower ones in the hand and then they eventually average out to being the same speed.

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Question 12 The surface of the planet Venus maintains a nearly constant temperature of 735 K. Convert the temperature of the surface of Venus to degrees Celsius.

$735°K-273.15=461.85°C$

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Question 13 The surface of the planet Mercury can reach temperatures as high as 450°C during the day, and as low as -170°C at night. This large variation occurs because Mercury does not have an atmosphere to trap the thermal energy during the night.

1. Convert the minimum night-time temperature on Mercury to kelvin. $-170°C+273.15=103.15°K$
2. Calculate the temperature range (the difference between the maximum and minimum temperatures) of the surface of Mercury. Provide your answer in kelvin. Maximum temp: $723.15°K$ Difference: $723.15°K-103.15°K=620°K$