Thermodynamics and Heat Transfer Lecture Notes

Flashcards to help review concepts in thermodynamics, heat transfer, and related physics topics.

What does it mean for two systems to be in thermal equilibrium?

No heat flow occurs between them and they are at the same temperature.

Give an example of a physical property that varies with temperature.

The volume of water varies with temperature and is used to measure temperature with a thermometer.

Why does the column of alcohol in a thermometer drop slightly when placed in a hot liquid?

The alcohol initially contracts due to the temperature difference before it starts expanding as it warms up.

What is the final equilibrium temperature when boiling water is added to a cup at room temperature?

The final temperature will equal the mass-weighted average of both the boiling water and the surrounding environment.

What is the significance of Pyrex® glass cookware regarding thermal stress?

Pyrex® has a small coefficient of linear expansion, making it less susceptible to breakage from uneven cooling.

What happens to biological cells when water freezes?

About 10% to 30% of cells can burst due to the 9% volume expansion of water as it freezes.

Should a metal peg be inserted when the block is colder or hotter?

The block should be colder than the peg to allow for expansion and a tight fit.

Why is running hot water over a tight metal lid on a glass jar helpful?

The hot water expands the metal lid slightly, making it easier to remove.

Calculate the mass of a mole of people if the average mass is 60 kg.

A mole of people weighs about 3.612 × 10^25 kg, which is vastly greater than the mass of Earth.

Convert 39.0ºC to Fahrenheit.

The Fahrenheit temperature is 102.2ºF.

Why are weather station thermometers shielded from sunlight?

To accurately measure air temperature without interference from direct heat.

What is the net heat transfer for an 80,000-L pool that increases in temperature by 1.50ºC?

The net heat transfer is 450 kJ, given the heat capacity of water.

What is the frost damage threshold for plants in Fahrenheit?

The frost damage threshold is 28.0ºF, which is equivalent to 255.37 K.

Convert 68.0ºF to Celsius.

The temperature is approximately 20.0ºC.

What is the Fahrenheit temperature of a tungsten light bulb filament at 2900 K?

The Fahrenheit temperature is approximately 4962ºF.

How much will the height of the Washington Monument decrease at -10.0ºC?

The height will decrease due to thermal contraction, calculated using the thermal expansion coefficient.

How does the Eiffel Tower's height change with a 15ºC temperature increase?

It becomes approximately 18.9 cm taller, using steel's thermal expansion formula.

What causes the level of coffee in a cup to drop as it cools?

The drop is primarily due to escaping air bubbles, not thermal contraction.

What is the gauge pressure in car tires when the temperature drops from 35.0ºC to -40.0ºC?

The pressure can be calculated using the ideal gas law, resulting in decreased gauge pressure.

Describe heat transfer related to temperature.

Heat transfer occurs when there is a temperature difference, flowing from higher to lower temperatures.

Identify a situation in which heat transfer occurs.

Cooking food involves heat transfer from hot surfaces to the food.

How much greater is the temperature change of a car brake from 2v compared to v?

The temperature change is four times greater since kinetic energy is proportional to the square of speed.

Why are cloudy nights warmer than clear nights?

Clouds trap heat, preventing it from radiating into space, creating a warmer microclimate.

How much heat transfer is required to sterilize a 50.0-g glass baby bottle from 22.0ºC to 95.0ºC?

The heat transfer required can be calculated using Q=mcΔT.

Calculate the temperature increase from rubbing hands together with specific friction force.

The average increase in temperature can be calculated using work done against friction.

Calculate the specific heat of a 0.250 kg block heated from 20.0ºC to 65.0ºC.

Specific heat can be calculated using the formula Q=mcΔT with known energy added.

What is the expected ratio of masses when equal heat is transferred into copper and water?

The mass ratio will reflect their differences in specific heat.

Describe the change in kinetic and potential energy when running down stairs and stopping.

Kinetic energy decreases, while gravitational potential energy is converted into thermal energy.

Identify energy forms transferred during basking in sunlight, eating, and using an elevator.

(a) Heat transfer; (b) Internal energy; (c) Work done.

What is the internal energy change of a car if 12.0 gal of gasoline is added?

The internal energy increases based on the energy content of gasoline.

Calculate the heat transfer from a system decrease of internal energy and work done.

Heat transfer is calculated as Q = ΔU + W.

Describe the energy change in a system that does work while heat is transferred out.

The internal energy decreases as heat is lost to the surroundings.

Why does a stiff material vibrate at a higher frequency than a spongy one?

Stiff materials have higher elasticity and restore force, resulting in higher vibrational frequencies.

Explain the bouncing trailer of a truck on the highway.

A happier trailer bounce indicates it is likely heavily loaded.

Should modified cars have stiffer springs?

Yes, to maintain stability and handling for the reduced clearance.

When moving to a city with greater gravity, should a pendulum be lengthened or shortened?

Shortened, to maintain the same period in a stronger gravitational field.

Give examples of a transverse wave and a longitudinal wave.

Transverse: light waves; Longitudinal: sound waves.

Why is it important to connect stereo speakers the same way?

Reversed connections cause phase cancellation, leading to poor sound quality.

What is the force constant of a spring scale that stretches 8.00 cm for a 10.0 kg load?

The force constant can be found using Hooke’s Law.

Calculate the effective spring constant of a bathroom scale depressed 0.75 cm by a 120 kg load.

The effective spring constant can be calculated using F= kx.

How far does a pickup truck's springs compress under a 1000 kg load?

Depression is calculated using the force constant and Hooke's law.

Calculate the frequency of a tuning fork with a 2.50 × 10-3 s period.

Frequency is the inverse of the period.

What force constant is needed for a 0.0150-kg mass in a cuckoo clock for 0.500 s?

The force constant can be derived from the properties of oscillation.

How much mass must be added to a 0.500 kg mass to change the oscillation period to 2.00 s?

Mass change is calculated using the form of the oscillation period equation.

What is the period of a pendulum with a 1.00 m length?

Calculated using T = 2π√(l/g).

Calculate the change in energy in a shock absorber of a car with a 1500 kg mass compressing 2 cm.

Potential energy change can be calculated using spring equations.

How long does it take light to travel 305 m?

Speed of light and distance give travel time.

How long does normal sound take to travel 305 m?

Using sound speed equations, calculate the time.

Explain whether you see or hear lightning first.

You see lightning first because light travels faster than sound.

What is the human ear's sensitivity change in decibels?

About ±3 dB translates to changes in perceived intensity.

What is the speed of sound at 56.0ºC?

Calculated using the temperature dependence on sound speed.

Convert sound intensity of 91.0 dB to watts per meter squared.

Use the formula for sound level to find intensity.

What sound intensity level in dB is produced by 4.00 × 10−2 W/m2?

Calculate using the sound intensity level formula.

What is the frequency of a wave with a wavelength of 0.10 m?

Use the speed of sound and wavelength relation to find frequency.

What sound intensity is 7.00 dB lower than 4.00 × 10–9 W/m2?

Intensity can be deduced from sound level differences.

How much more intense is a sound level 17.0 dB higher than another?

Intensity ratio can be calculated from sound level differences.

What happens when one sound is 23.0 dB less than another?

Calculate intensity ratios based on sound level differences.