Quantum Mechanics – Newtonian Mechanics Comparison

Quantum mechanics differs from Newtonian Mechanics in various aspects. These differences between the Quantum Mechanics and Newtonian Mechanics are discussed here. The major difference exist between them is due the fact that Quantum mechanics has probabilistic approach and Newtonian mechanics has deterministic approach towards any problem. This understanding is useful for many physics enthusiasts , Graduate physics students and aspirants writing competitive examinations involving Physics , Quantum Physics and Newtonian Physics.

Quantum Mechanics – Problem statement

Question : Bring forth the salient differences in the approach for solving a physics problem involving Quantum Mechanics and Newtonian Mechanics.

Solution

The Newtonian Mechanics mainly focuses on the macroscopic level in its applications where as the Quantum Mechanics focuses on the microscopic domain. This major difference of level of focus towards a physics problem in both cases differentiate them. But it is to understand here that both of these approaches work towards providing the best possible solutions to the universe problems. Now let us take up each one separately and discuss about them in following sections.

Newtonian Mechanics

Let us understand the Newtonian Mechanics approach with a suitable practical example.

Let us assume that we are required to find out a Centrifugal Pump capacity to pump a particular quantity of fluid from ground level to a determined height in a process industry or in a residential complex.

To solve above problem in Newtonian Mechanics, based on the deterministic calculations of continuous forces acting on a given system the pump capacity is finalized . This is a simplified approach when compared with discrete molecular level calculations.

In this approach, the fluid is treated as continuous smooth medium. The friction losses in the system design are calculated using the macroscopic variables like pipe roughness, fluid viscosity by obtaining the Reynolds number. The energy transfer is converting Kinetic Energy into pressure head using the impeller. The impeller by pushing the fluid continuously, does the mechanical work in a smooth manner. The power calculations are made from the given equations on deterministic manner as,

Power required= Product of density of fluid , Flow rate, Pump Head and Acceleration due to gravity.

The above value obtained as power is divided by suitable efficiency factor of the pump and motor assembly.

From the above example it can be understood that the approach is simple, continuous and macroscopic application.

Now let us take the same example discuss about approach in case of Quantum Mechanics in the following section.

Quantum Mechanics

The same example what we have taken in case of Newtonian Mechanics be illustrated using the principles of Quantum Mechanics.

Here the fluid is not treated as continuous smooth medium but is treated as collection of trillions of discrete molecules. The approach is to take the statistical average of the trillions of discrete molecules.

The friction losses are not calculated on the basis of roughness of pipe and viscosity of fluid but is determined by calculating the electromagnetic scattering of fluid molecules with wall atoms along the wall of fluid flow.

The energy transfer takes place by the impeller in the form of quantum packets ( Like Photons) during collisions of trillions of discrete fluid molecules.

The power calculation is also not straight forward as in Newtonian Mechanics . It is the statistical summation of momentum states of the trillions of individual particles.

Hence as above the application of Quantum Mechanics is cumbersome in case of above problem. But in many cases where continuum can not be finalized and discrete data variable , there Quantum Mechanics take a leap.

Suitability of of Quantum Mechanics and Newtonian Mechanics

Quantum Mechanics is suitable where discrete molecular calculations are required at micro level. The most suitable example for application of Quantum mechanics is in designing of modern smart phone processors.

The Newtonian Mechanics is suitable where macroscopic calculations are involved. The most modern application is in case of air craft trajectory calculations involving mass, gravity, velocity etc.

Conclusion

In one sentence we can conclude that in case of planetary system, Newtonian Mechanics is used in mapping the orbits of the planets where as the Quantum Mechanics maps the probabilistic behavior of atoms that build them.

Finally the Newtonian Mechanics is macroscopic application of deterministic approach and Quantum Mechanics is microscopic application of probabilistic approach for the same problem in Physics.

Depending upon the ease and requirement the application of Quantum Mechanics and Newtonian Mechanics is finalized.

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