# Newton Laws of Motion

Newton’s First Law of motion:

It states that ” Everybody in this universe continues to be in the state of rest or motion unless an external force is applied on it.” It is also known as law of inertia.

Some of the examples of Newton’s first law of motion are:

• When mango tree is shaken, the mango falls.
• A ball thrown upward on a moving train returns to the thrower.
• An athlete runs for sometime before he takes a long jump.

Second Law of motion:

It states that the rate of change in linear momentum is directly proportional to the external force applied on it and takes place in the direction of force.

If P is the momentum and the rate of change in momentum is dP/dt.

$$\text{F} = \frac{\text{dP}}{\text{dt}}$$

$$\text{F} = \frac{\text{d(mv)}}{\text{dt}}$$

$$\text{F} = \text{m}\frac{\text{dv}}{\text{dt}}$$

$$\therefore \text{F = m.a}$$

So, according to this law, force is the product of mass and acceleration.

Unit of force: The SI unit of force is Newton and CGS unit is dyne.  It is a vector quantity.

Third law of motion:

It states that, “To every action, there is equal but opposite reaction.”

Some of the examples of Third law of motion:

• People get heavy injury in the road accident.
• Mechanism of walking in the street.
• Mechanism of firing the bullet.

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