 Archimedes Principle : the apparent loss in weight of a wholly or partially submerged body in a fluid, is equal to the weight of the fluid displaced by it.

Newton`s Law of Gravitation : All particles of matter mutually attract each other by a gravitation force which is proportional directly to the product f their masses and inversely t o the square of the distance between them.

Newton`s FIRST Law of Motion : A body in a state of rest cannot move by itself or a body in a state of uniform motion cannot stop by itself unless an external force acts upon it to change its state of uniform motion.

Newton`s  Second Law of Motion : The rate of change of momentum of a body is directly proportional to the force applied and takes place in the direction in which the force acts.

Newton`s Third Law of Motion : To every action there is equal and opposite reaction.

Newton`s Law of Cooling : The rate at which the body cools or loses heat to its surrounding is directly proportional to the excess  of mean temperature of the body provided the excess is small.

Law of Flotation of Body : A body when wholly or partly immersed in a fluid experience an upthrust which is equal to the weight of the fluid displaced by the floating body .

Law of Conservation of Energy : Energy can neither be created nor be destroyed , but can be converted from one form to another . the sum total of all the energy  in the system remains constant.
Law of Conservation of mass or matter : Matter can neither be created nor destroyed. T be the sum total of all the matter or mass in a system always remains constant without any increase or decrease on their quantity.

Einstein`s Law of the equivalence of mass and energy : According to him , the mass and energy are inter convertible aspects of the same property ,and when a body gives up energy, it also losses mass. Numerically this law has been stated as E=mc2   .

Principle of Lever: In case, of equilibrium of a rod (called lever) under two forces, the forces are to each other inversely as the lengths of lever arms from the fulcrum , i.e. the products of the forces  by the length of their lever arms are equal .

Ampere`s swimming rule : If a man sets himself floating in the direction of the current facing the coil, then the north of a magnetic needle is directed towards his left hand.

Laws of Refraction of Light:
I. A ray of light pains from a rarer medium into a denser medium is deviated towards the normal at the point of striking the common surface of two media. The ray is deviated away from the normal when it passes from denser to the rarer media.
II. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is called the refractive index of the second medium with respect to the first. The second Law is called the SNELL`S LAW.