Mechanics (Part – 2)

As the fast-moving train passes, the air between the train and the man starts moving rapidly. According to Bernoulli’s Principle, when the velocity of a fluid (like air) increases, its pressure decreases.

• On the side away from the train, air is relatively still → higher pressure

• On the side near the train, air is moving fast → lower pressure

This difference in air pressure causes a net force towards the train, which is why the man feels a pulling effect.

Types of Translatory Motion:

1. Rectilinear Motion
   Motion along a straight line
   Example: A car moving on a straight road

2. Curvilinear Motion
   Motion along a curved path
   Example: A ball thrown in air (projectile motion)

This law, which is a foundational principle in physics, states that an object at rest will remain at rest,

and an object in motion will remain in motion with the same speed and in the same direction unless acted upon by a force.

Therefore, even when there is no acceleration, velocity, or motion at rest, an object can still have energy.

Potential energy is the stored energy of an object due to its position or configuration.

Formula of Gravitational Potential Energy:

$$PE=mgh$$

Where:

• PE = Potential energy (in joules, J)

• $m$ = Mass of the object (in kg)

• $g$ = Gravitational acceleration (9.8 m/s² on Earth)

• $h$ = Height of the object from the ground (in meters)

It is also called the law of inertia

Examples of Newton’s First Law:

1. A book on a table stays at rest until you push it.

2. A moving car will keep rolling unless brakes (friction force) are applied.

3. A football will not move unless kicked (external force).

It is also called the law of inertia

Examples of Newton’s First Law:

1. A book on a table stays at rest until you push it.

2. A moving car will keep rolling unless brakes (friction force) are applied.

3. A football will not move unless kicked (external force).

It is also called the law of inertia

Examples of Newton’s First Law:

1. A book on a table stays at rest until you push it.

2. A moving car will keep rolling unless brakes (friction force) are applied.

3. A football will not move unless kicked (external force).

Explanation:

• The passengers were initially at rest along with the bus.

• When the bus starts suddenly, its body moves forward.

• But the passengers’ bodies tend to remain at rest due to inertia.

• As a result, they appear to fall backward relative to the motion of the bus.

Mathematically, it can be represented as

F = ma.

where

F = net force acting on it,
M = mass of the object,
A = the acceleration of an object,

• This law describes how forces affect the motion of an object and how they can change the velocity and direction of an object's movement.
• It provides a quantitative definition of force by stating that force is equal to the mass of an object multiplied by its acceleration.