What are two main tools of Physics?

Hint: In order to solve this question, we should know that Physics is the branch of science that deals with the study of all physical phenomena happening in nature and most importantly the study of matter and energy and to study the various phenomena, it needs some basic mathematical structure and laws which govern almost whole physics. Here, we will discuss two main tools of physics.

Complete answer:
The fundamental laws of motion which are known as Newton’s laws of motion are one of the most important tools in Theoretical Physics, almost every aspect of classical mechanics can be explained using Newton’s laws of motion which are
1. A body will remain at rest or in motion forever until no external force is applied to it.
2. The Force applied to a body is equal to the change in momentum of a body
3. For every action force, there is an equal and opposite reaction force.

Another most important tool in physics is Calculus which includes Differentiation, Integration, and Limits. Almost every equation in physics needs to be written in a manner such that its mathematical form represents the nature of the phenomenon completely and in order to do this many equations are written in differential and integral form which makes physics equations not only elegant but it makes easier to understand the nature what they represent and their solutions.

For example, Gauss law in electricity is written in integral form as
$\int {E.ds = \dfrac{q}{{{\varepsilon _0}}}} $
which clearly indicates that the total electric flux around the given surface is equal to the charge divided by relative permittivity of free space.

Hence, Laws of motion and Calculus are the two main tools of physics that are used in each area of physics to study the nature of the physical phenomenon.

Note: It should be remembered that Calculus is the branch of mathematics that involves the study of continuous change of any given function and since the physics of any physical event need to understand in terms of its change in past, present, and future Calculus is widely used in each field of physics from Classical mechanics to Quantum Mechanics.