Classical Physics

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Classical Physics

Contributions by Anika Jones Fall 2022

Classical physics encompasses the theories of mechanics, electromagnetism and thermodynamics that help explain a large part of the everyday things that go on around us on a macroscopic scale, which predates Modern Physic theories of quantum and relativity that explains things that are on the smaller, microscopic level.

In classical physics, observations about things can be seen using the human senses. For example, Newton’s observation that gravity caused things to fall to the ground leading to his three physics laws that are still relevant today. Classical physics helps to answer the whys about the things that we observe and experience in the world around us, from the path of the sun in the sky to the reaction of boiling a pot of water.

Classical physics laid the groundwork for modern physics theories to understand those things around us that we can not see in the traditional way but observed behaviors that are happening on a microscopic level.

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Be sure to show all steps in your solution and include diagrams whenever possible


(Classical Mechanics) Find Velocity from Position

A particle's position is given by: r = A(e^(alpha*t)i-hat + e^(-alpha*t)j-hat), where A and alpha are constants. Find the velocity.

v = dr/dt

  = A(e^(alpha*t)i-hat - e^(-alpha*t)j-hat)

vx = A(alpha)e^(alpha*t) vy = -A(alpha)e^(alpha*t)

the magnitude of v is:

v = sqrt(vx^2 + vy^2)

 = A(alpha)sqrt[e^(2(alpha)t) + e^(-2(alpha)t)]



Air with a relative humidity of 30% at 20°C is pumped into a container. What is the maximum pressure inside the container so that water does not condense on the inside of the container? Assume the air temperature inside the container is 20°C.

Solution: For air at atmospheric pressure and at a temperature of 20°C, containing water vapor where the relative humidity is 30%, the water vapor's partial pressure is Pw = 0.30×Pg (according to the definition of relative humidity), where Pg is the pressure of saturated water vapor.

Referencing a thermodynamics table containing the properties of saturated water (H2O), Pg = 0.002338 MPa. Therefore, Pw = 0.30×0.002338 = 0.0007 MPa. We then calculate the air pressure inside the container so that Pw = Pg. Thus the partial pressure of the water vapor inside the container is equal to the pressure of saturated water vapor (at 20°C).

When the air pressure is increased by some multiple M, then the partial pressure of the water vapor present in the air will increase by the same multiple M (based on Dalton's law of partial pressures). So, M = 0.002338/0.0007 = 3.34.

Finally, the maximum pressure inside the container is 3.34×(atmospheric pressure) = 340 kPa, approximately, for atmospheric pressure = 101.3 kPa. At this pressure the water vapor will begin to condense inside the container (at the dew point temperature of 20°C). If water condenses inside the container it can cause corrosion or mold growth. To prevent this keep the pressure inside the container to less than 340 kPa, so that water condensation doesn't occur.



This topic helped to differentiate between modern physic theories and classical physic theories. I was able to understand where classical physics stops, and modern physics begins. It put things into perspective with usage of equations and application on the macroscopic scale versus the microscopic scale.

As a physics major, this distinguish is important in the approach to solving problem for large bodies that are moving slower than the speed of light versus subatomic particles moving at the speed of light.

Classical physics theories are still the basis for theories in modern physics, for example in classical physics any frame moves at a constant velocity if there is no external force or the object is at rest, in modern physics (special relativity) an inertial frame is a frame of reference when a free object experiences zero net force and moves at constant velocity relative to the observer.

Industrial application of classical physics can be seen in electric motors, elevators, moving floors to escalators.


Classical Physics predates 1900 physics theories that help us understand phenomena around us, all thanks to works of Sir Isaac Newton, Galileo Galilei, and James Maxwell just to name a few. From their observations and research, we have a better understanding of how and why things operate the way they do around us that led to technological advances that we enjoy today in making a way of life easier.

Without any fancy and high-tech equipment, these scientists use simple observations and equipment to build the foundation of physics as we know it today that has been proven over hundreds of years to still be valid. From Newton’s law that force is equal to mass times acceleration to Maxwell’s equation for electromagnetism. Without their contributions our world today would look a lot different.

See also

For further exploration, see related topics in classical mechanics, electromagnetism, and thermodynamics. These topics are what make up the theories of classical physics.

Further reading

1. Jefimenko, O. (1989). Electricity and Magnetism. An Introduction to the Theory of Electric and Magnetic Fields (2nd ed.). Electret Scientific. ISBN 978-0917406089. Jefimenko, Oleg D.; Major, Schwab S. (November 1967). "Electricity and Magnetism". American Journal of Physics. 35 (11): 1100–1101. Bibcode:1967AmJPh..35.1100J. doi:10.1119/1.1973766. hdl:10821/2745. ISSN 0002-9505.

2. Morin, David (2005). Introduction to Classical Mechanics: With Problems and Solutions. Cambridge University Press. ISBN 9780521876223.

3. Taylor, John (2005). Classical Mechanics. University Science Books. ISBN 189138922X.

4. Van Ness, H. C. (1983). Understanding Thermodynamics. Dover Publications. ISBN 978-0486632773.

External links


1. Harris, Randy. Modern Physics. San Francisco, CA: Pearson 2008. Print.

2. Kleppner, Daniel, and Kolenkow, Robert. An Introduction to Mechanics. Cambridge University Press 2010. Print.