In classical mechanics, how many fundamental laws of motion were formulated by Sir Isaac Newton?

Introduction / Context:
The original question in the database was loosely worded as "How many laws of physics are there?", which is too vague because physics contains many different laws. Applying the recovery-first policy, it is natural to interpret this as a question about Isaac Newton's famous laws of motion, which are fundamental in school-level mechanics. These laws describe how forces affect the motion of bodies and are usually introduced early in physics courses.

Given Data / Assumptions:
- We interpret the question as referring to Newton's laws of motion, not all laws of physics.
- Options are four numbers: 5, 4, 3 and 2.
- Standard school physics recognises three distinct laws of motion formulated by Newton.

Concept / Approach:
Newton's first law discusses inertia and states that a body remains at rest or in uniform motion in a straight line unless acted upon by a net external force. The second law provides the relation between force, mass and acceleration, often written as F = m * a. The third law states that for every action there is an equal and opposite reaction. These are collectively known as the three laws of motion. There are not two, four or five such laws in basic mechanics.

Step-by-Step Solution:
Step 1: Recall the statement of Newton's first law (law of inertia). Step 2: Recall the statement of Newton's second law (relationship between force and acceleration). Step 3: Recall the statement of Newton's third law (action and reaction). Step 4: Count the number of distinct laws of motion: there are three. Step 5: Match this number with the given options and select 3 as the correct answer.

Verification / Alternative check:
Any standard physics textbook lists Newton's laws of motion as three separate principles. While there are many other laws in physics (for example, laws of thermodynamics, Maxwell's equations and conservation laws), when students are asked about "laws of motion" in basic mechanics, the universally accepted answer is three. This confirms that choosing three is consistent with accepted scientific and educational practice.

Why Other Options Are Wrong:
5: There are not five Newtonian laws of motion in basic mechanics courses.
4: Some students incorrectly think that because there are other laws in physics, the total must be four or more; however, Newton's motion laws are exactly three.
2: Newton formulated more than two laws describing motion, so this option is clearly too low.

Common Pitfalls:
A common mistake is to misread the question and think of "laws of physics" in general instead of the specific laws of motion. Another pitfall is to assume that additional concepts such as the law of gravitation are counted as motion laws, which they are not. To avoid confusion, always link the phrase "laws of motion" to the three classical Newtonian laws introduced at the beginning of mechanics.

Final Answer:
Sir Isaac Newton formulated three fundamental laws of motion in classical mechanics.