Simple Definition of Newton’s Second Law (A Quick Look)

How many definitions are there in Newton’s second law of motion?

Well, there are so many concepts in Newton’s second law of motion.

(If you have read Newton’s second law, then you already know)

But if we talk about the definition of Newton’s second law then?

It’s simple.

There are only 2 definitions in Newton’s 2^nd law of motion.

Let’s understand these two definitions of Newton’s second law of motion. (Step by Step)

In terms of object’s acceleration,

Newton’s second law of motion can be defined as:

“The acceleration is directly proportional to net force applied and inversely proportional to mass of the object”

In terms of Momentum, 

Newton’s second law of motion states that:

“The net force applied on the body is equal to its rate of change of momentum and takes place always in the direction of force applied”

Understand the definition of Newton’s second law with example

Don’t worry, if you have not understood the above two statements.

I’ll make this simple.

Let’s understand the above 2 definitions of newton’s second law in a practical way. 

(One by One)

Definition #1

In terms of object’s acceleration,

Newton’s second law of motion states that:

“The acceleration is directly proportional to net force applied and inversely proportional to mass of the object”

This statement means that, 

“Acceleration” of any object depends upon both “force” as well as “mass“.

I’ll explain how. 

Simply think, what happens when you hit the ball by the bat?

How Newton’s second law of motion works here?

See this,

Why does the player have to apply more force to hit this ball?

It’s simple.

The reason is football. (As the football has more mass, more force is required to hit that ball)

In short, acceleration of football inversely depends upon its mass.

(More the mass the object has, the more net force is required to accelerate that object)

In this case, 

Why does the player have to apply less force to hit this ball?

It’s simple.

The reason is the tennis ball. (As the tennis ball has less mass, less force is required to hit that ball)

In short, acceleration of football directly depends upon the net force applied on it.

(If the object has less mass, less force is required to accelerate that object)

Therefore, 

Acceleration of any object depends upon both mass as well as force.

This thing indicates the presence of Newton’s second law of motion.

Definition #2

In terms of Momentum, 

Newton’s second law of motion can be stated as:

“The net force applied on the body is equal to its rate of change of momentum and takes place always in the direction of force applied”

Before understanding the above statement, let’s first understand the definition of momentum.

So, what is momentum?

“Momentum is that quantity by which how much amount of motion present in the body can be known”

Or

Simply, Momentum is defined as the product of mass and velocity.

The formula for the momentum is, 

Momentum (p) = mass (m) × velocity (v)

Its symbol is ‘p‘ and its unit is kg m/s².

Momentum of any object depends upon both mass as well as velocity.

Let’s make this simple.

Let,

F_net = net force applied to the body

m (v – u) / t = rate of change in momentum

mu = initial momentum of the object 

mv = final momentum of the object 

u = initial velocity of the object

v = final velocity of the object

t = time

So, we get the following equation for newton’s second law:

F_net = m (v – u) / t

F_net = (mv – mu) / t

Now read the above statement of Newton’s second law in terms of momentum.

“The net force applied on the body is equal to its rate of change of momentum and takes place always in the direction of force applied”

Always remember, 

(More the momentum the object has, the more net force is required to stop its motion)

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Don’t you think, is easy to remember the definitions of Newton’s second law of motion?

(Let me know by leaving a comment)