Newton’s laws of motion are some absolute laws that define much of the actions that we witness every day. The daily phenomena are influenced and their actions are mostly consequences of Newton’s laws of motion.
Now coming to the laws,
Newton’s First Law of motion
“Newton’s First law of motion states that an object at rest will stay at rest, and an object in motion will stay in motion unless acted on by an external unbalanced force.“
The literal meaning of this law is that without force no object can change its position or state. This suggests that there must a certain entity X that acts on all bodies so that it does not change its state. This unknown X is known as inertia. It tends to keep the object in its original state and hence resist any change of motion.
That’s why the first law is also known as the law of inertia.
This means that when an object is lying idly on some surface, it will not until and unless force is applied. This also means that a moving bus cannot stop until breaks are applied or simply until a force is applied.
Mathematically it means,
Summation F = 0
i.e. dv/dt=0 (where v= velocity and t= time)
Newton’s Second Law of motion
“Newton’s Second Law of motion states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force.”
As we know, by definition the rate of change of momentum signifies acceleration. Hence, the second law simply means that acceleration is directly proportional to applied force( in the same direction).
This means that the acceleration of certain something increases as soon as the force on it increases in its direction.
For example, in hockey when you shoot the ball with a force the acceleration of the moving ball increases and changes into the direction of the applied force.
The definition also means that that force is dependent on acceleration,
or simply F=ma, where ( F= applied force, m=mass, a=acceleration)
F is directly proportional to m and a.
Hence, a greater force is required for a greater mass object.
That is why when we push a rock A and another Rock B with the same force, then Rock B will move lesser compare to A if the mass of B is greater than A.
Newton’s Third Law of motion
“Newton’s Third Law of motion states that for every action there is an equal and opposite reaction.”
This law is also known as the action-reaction law. The meaning of this law is that there is always an opposing force to every applied action.
A simple example of this is a book lying idly on a table.
There book is in that state as the book applies certain force/weight to the table, and in return, the table applies some force back to the book.
Thus, Newton’s law is applicable anywhere and everywhere.
You might understand the definition in whatever way you wish. But the scientific definitions must not be altered.