Question

Show that the second law of motion is the real law.

Answer 1

In order to prove the above sentence, we need to explain that both the first and third law of motion are contained in the second law of motion. If a body is art rest, it has no acceleration, no force is acting on it. If it is moving with constant velocity, it continues till some other force stops or resits.

Complete step by step answer:
At present, the newton's second law states that the force acting on any body is equal to the product of mass of the body and the acceleration with which the given body is moving in the universe.
Now, when no force is acting on the body, when there’s absence of force,
The product of mass and acceleration of the body will be equal to zero. As mass of the body can never be zero, the only possibility is the acceleration to be zero. This means that the body will remain at rest, if there’s no force acting on it. This states the first law of motion.
Next, the third law states that in an isolated system, no force is acting as all the forces must cancel each other. It means that as many positive forces are present, the same number of negative forces are present to cancel them. This is newton's third law.

Note:
During the calculation of Newton's second law of motion, most of us write down the horizontal forces into vertical equations, this leads to disapproval of Newton's laws of motion. Hence, we need to be sure that the horizontal forces are taken in horizontal equations and the same goes for vertical forces.