Let me ask you a question, how many Newton’s laws are there?

Well, the correct answer is **5.**

Among these five laws,

Three laws are combined together which is further known to us as Newton’s three laws of motion.

These three newton’s laws of motion are:

**Law I –**Newton’s first law of motion

**Law II –**Newton’s second law of motion

**Law III –**Newton’s third law of motion

And the other two newton’s laws are:

**Law IV –**Newton’s law of cooling

**Law V –**Newton’s law of universal gravitation

**Don’t worry.**

I’ll make you understand all newton’s laws with practical examples.

(One by One)

Newton’s first law of motion

**According to Newton’s first law of motion, **

*“An object at rest remains at rest and object in motion remains in motion unless an **unbalanced force** acts on it”*

Let’s understand the above statement with a practical example, so you’ll get an **exact idea.**

See this,

If you have you noticed,

When the ball is simply lying on the ground, it will **not move on its own.**

Even while the ball is in motion, it will **not stop on its own.**

(If there is *no friction* along the surface)

In short,

Any object (whether in rest or in motion) will not change its behaviour, unless an **unbalanced force** acts on it.

**That’s all you need to understand** in Newton’s 1^{st} law of inertia.

*“An object at rest remains at rest and object in motion remains in motion unless an **unbalanced force** acts on it”*

If you want to see more examples of Newton’s first law of motion,

**Check out:** Real life examples of Newton’s first law

## Newton’s second law of motion

**According to Newton’s second law of motion,**

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

I know, it’s complicated.

Let’s understand the above statement with a practical example, so you’ll get an **exact idea.**

See this,

As the stone has **less mass,** it requires **less force** to accelerate further.

Therefore,

Acceleration of stone is **directly proportional** to net force applied on it.

On the other hand,

As the stone has **more mass,** it requires **more force** to accelerate further.

Therefore,

Acceleration of stone is **inversely proportional** to its mass.

That’s all you need to understand in Newton’s 2^{nd} law.

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

If you want to see more examples of newton’s second law of motion,

**Check out:** Real life examples of Newton’s second law

## Newton’s third law of motion

**According to Newton’s third law of motion,**

*“To every action, there is **always** an equal and opposite reaction”*

Newton has given the statement of the third law of motion in very **simple language.**

See this,

You have definitely understood the exact meaning of Newton’s 3^{rd} law of motion.

All you need to remember is,

*“To every action, there is **always** an equal and opposite reaction”*

That’s all you need to understand in Newton’s 3^{rd} law.

If you want to see more examples of newton’s third law of motion,

**Check out:** Real life examples of Newton’s third law

## Newton’s law of cooling

**According to Newton’s law of cooling, **

*“The rate of heat lost by a body is **directly proportional** to temperature difference of a body and its surroundings”*

So we can write as,

– dQ / dt ∝ ∆T

– dQ / dt = k ∆T

– dQ / dt = k (T_{2} – T_{1})

**dQ / dt = – k (T _{2}**

**– T**

_{1}**)**

This formula can be used to solve different numericals in Newton’s law of cooling.

Where,

dQ / dt = Rate of heat lost by a body

∆T = (T_{2} – T_{1}) = Temperature difference between the body and its surroundings

T_{1} = Temperature of the surroundings

T_{2} = Temperature of the body

k = positive constant which depends upon the area and nature of the surface of the body

Let’s understand the above mentioned statement of Newton’s law of cooling by considering one practical example.

See this,

As you can see,

When a cup of **hot tea** is left on the table, it cools down gradually.

Now,

To understand **how the body cools down** by exchanging heat with the surroundings,

See the graph of **temperature vs time **mentioned below.

Here, you can see how the temperature of the body falls down w.r.t time.

In short,

*Cooling rate of the body keeps on decreasing **as the temperature falls down.*

If you want to learn more about the formula, derivation of Newton’s law of cooling,

**Check out:** Formula used for newton’s law of cooling

## Newton’s universal law of gravitation

**According to Newton’s universal law of gravitation,**

*“Every particle attracts every other particle in the universe with a force which is **directly proportional** to the product of their masses and **inversely proportional** to the square of the distance between their centers”*

In mathematical terms,

** F _{g}**

**∝ m**

_{1}**m**

_{2} **F _{g}**

**∝ 1/d**

^{2}Therefore,

**F _{g}**

**∝ (m**

_{1}**m**

_{2}**) / d**

^{2} **F _{g}**

**= G (m**

_{1}**m**

_{2}**) / d**

^{2}Where,

F_{g} = Gravitational force

G = Universal gravitational constant

m_{1} , m_{2} = Masses of the two bodies

d = Distance between their centers

To understand the statement of Newton’s universal law of gravitation,

Let’s take one example.

Consider two balls having mass m_{1} and m_{2} as shown in the figure.

Let, d be the distance between their centers.

Now,

**According to Newton’s law of gravity,**

*Both these balls will apply force on each other. (i.e. **force of attraction**)*

See this,

**Always remember,**

Forces on both the balls have the same value and this force always acts along the line joining them.

The value of force is **F**_{g}** = G (m**_{1}** m**_{2}**) / d**^{2}

Here, G is known as the **universal gravitational constant**.

It’s value is,** G = 6.673 × 10 ^{-11} Nm² / kg²**

**........**Don’t you think it is easy to remember all Newton’s laws?

(Let me know by leaving a **comment**)

If you want to **read more** about the Newton’s laws,

**You can check here:**

**Newton’s laws of motion**

**Newton’s first law of motion**

Newton’s first law example

**Newton’s second law of motion**

Newton’s second law example

Newton’s second law equation

Definition of newton’s second law

**Newton’s third law of motion**

Newton’s third law example

**Newton’s law of cooling**

Newton’s law of cooling formula

**Newton’s law of inertia**

Newton’s law of inertia examples

**Newton’s universal law of gravitation**