Common Misconceptions about Laws and Principles in UPSC Physics Optional


Newton's Laws of Motion are fundamental principles in classical mechanics. However, there are a few common misconceptions related to these laws:

- First Law (Law of Inertia): Some students believe that an object at rest will always remain at rest unless acted upon by an external force. However, this law also applies to objects in uniform motion. According to the first law, an object will continue to move with a constant velocity unless acted upon by an external force.

- Second Law (Law of Force and Acceleration): Many students mistakenly assume that the force acting on an object is directly proportional to its velocity. However, the second law states that the force acting on an object is directly proportional to its acceleration, not velocity.

- Third Law (Law of Action and Reaction): One common misconception regarding this law is that the forces in an action-reaction pair act on the same object. In reality, the action and reaction forces act on different objects, and they are equal in magnitude and opposite in direction.


Ohm's Law relates current, voltage, and resistance in an electrical circuit. However, there are a few common misconceptions associated with it:

- Resistance is independent of temperature: Some students mistakenly believe that resistance in a conductor remains constant regardless of temperature. In reality, the resistance of most conductors increases with an increase in temperature.

- Ohm's Law is applicable to all materials: Ohm's Law holds true for most metallic conductors, but it may not be applicable to all materials. Semiconductors and other non-ohmic materials may not follow Ohm's Law.


Bernoulli's Principle describes the relationship between the speed of a fluid and its pressure. However, it is often misunderstood in the following ways:

- Incorrect explanation of lift: Some students mistakenly believe that Bernoulli's Principle is solely responsible for the generation of lift in an airplane wing. In reality, the generation of lift is a complex phenomenon involving various factors such as angle of attack and airfoil shape.

- Equal transit time fallacy: According to this fallacy, students believe that in a horizontal flow, the fluid particles traveling over the top and bottom surfaces of an airfoil must meet at the trailing edge at the same time. However, this is not true, as the particles that follow different paths can still meet at the trailing edge simultaneously.

It is crucial to understand these misconceptions and have a clear understanding of the laws and principles to excel in the UPSC Physics Optional examination.