Question

State Newtons first law of motuon and also deduce it using second law

Answer 1

Newton's Laws of Motion

Newton's First Law of Motion

It states that any object at rest or in uniform motion along a straight line can't change its state of rest or of uniform motion along a straight line until an external, unbalanced force acts on it. This law is also called the Law of Inertia.

Newton's Second Law of Motion

It states that the change in momentum of any object is directly proportional to the force applied and is in the direction of the force. Let's derive an expression for this law.

Consider an object of mass m, moving with initial velocity u. Let a force F be applied on it to change its velocity from u to v in time t to produce an acceleration a. Let it cover a distance of s meters.

Now, Initial momentum of the object (p1) = mu;

Final momentum of the object (p2) = mv;

Change in momentum = (p2 - p1) = mv - mu or m(v-u)

Rate of change of momentum = m(v-u)/t

But, we know that (v-u)/t = acceleration of the object, ie, a in this case.

So, rate of change of momentum = ma

Also, we know that Rate of change of momentum is directly proportional to the force applied. So,

F ∝ ma

or, F = kma, where k is the constant of proportionality and its value is one.

So, F = kma = 1(ma) or simply, F = ma.

The above expression in bold is the expression for Newton's second Law of Motion.

Deducing the Law of Inertia from the Second Law

We know that F = ma. Also, a = (v-u)/t. So, F = m(v-u)/t

Thus, Ft = mv - mu

Further, if F = 0N, mv - mu = 0 or mv = mu or v = u

This is what the First Law of motion is.

Thanks for the question!

Answer 2

First Law Of Motion. Isaac Newton's first law of motion, also known as the law of inertia, states that an object at rest will stay at rest and an object in motion will stay in motion with the same speed and direction unless acted upon by unbalanced forc force
Newton's second law of motion pertains to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object.