Work, Energy & Power in ONE SHOT for NEET 2026 by Saleem Sir

The chapter Work, Energy, and Power holds strong importance in physics preparation for exams like NEET 2026. Questions from this unit appear regularly and cover both basic understanding and numerical application. 

A structured approach to this chapter helps in building clarity across multiple concepts such as force, motion, and energy transfer. Work, Energy & Power in ONE SHOT for NEET 2026 by Saleem Sir will help in revising this core topic for upcoming exam.

Introduction to Work

Work is said to be done when a force acts on an object and causes displacement. Both force and displacement must be present.

The mathematical expression for work done by a constant force is:

W=Fdcos⁡θ

Here,

• F is the applied force

• d is the displacement

• θ is the angle between force and displacement

Nature of Work

Work can be classified into three types:

• Positive Work: When force and displacement are in the same direction

• Negative Work: When a force acts opposite to the displacement

• Zero Work: When force is perpendicular to displacement

An important point is that work depends on displacement, not on the path followed. This means work done by a constant force remains the same for different paths between the same points.

Work Done by Multiple Forces

When several forces act on a body, the work done by each force is calculated separately. The total work is the sum of all individual works.

Net work can also be calculated using the net force acting on the body.

Example Concept

If a block moves under:

• Applied force forward

• Friction backward

Then:

• Work by applied force is positive

• Work by friction is negative

Normal force and gravity often do zero work when the displacement is horizontal.

Work-Energy Theorem

The work-energy theorem connects force and motion. It states that the net work done on a body is equal to the change in its kinetic energy.

This theorem helps in solving problems without directly using force and acceleration equations.

Work Done by Variable Force

In many real situations, force is not constant. It may depend on position or time. In such cases, work is calculated using integration.

The general form is:

This means work is the sum of small contributions over displacement.

Graph Method

Work done by a variable force can also be found from the area under the force vs displacement graph.

• Area above axis → positive work

• Area below axis → negative work

This method is useful in numerical questions.

Indirect Use of Work-Energy Theorem

Sometimes velocity is given as a function of time or position. In such cases, instead of calculating force, the change in kinetic energy can be used directly.

This approach reduces calculation steps and helps in solving complex problems faster.

Work Done by Spring Force

Spring force follows Hooke’s Law:

F=−kx

The work done by a spring when it is stretched or compressed is:

Important observations:

• Work done by spring is negative when it opposes motion

• The formula works for both compression and extension

• It depends on the square of displacement

Work Done by Gravity

Gravity is a conservative force. Work done by gravity depends only on vertical displacement.

W=±mgh

• Positive when the object moves downward

• Negative when the object moves upward

The path does not affect the work done by gravity.

Vertical Circular Motion

In vertical circular motion, a particle moves in a circular path under gravity.

Key Points:

• Tension changes at different points

• Velocity changes along the path

• Gravity does work, but tension does no work

Minimum velocity at the lowest point to complete the circle:

At different points:

• Tension is maximum at the bottom

• Tension is minimum at the top

Work-energy theorem is used to solve most problems in this topic.

Power

Power measures how fast work is done.

Where:

• P is power

• F is force

• v is velocity

Types of Power

• Average Power: Total work divided by total time

• Instantaneous Power: Power at a particular instant

Power is useful in understanding machines, engines, and motion systems.

Conservative and Non-Conservative Forces

Conservative Forces

• Work depends only on the initial and final positions

• Work done in a closed path is zero

Examples:

• Gravitational force

• Spring force

Non-Conservative Forces

• Work depends on the path

• Energy is lost in the form of heat or friction

Example:

• Friction

Potential Energy

Potential energy is associated with position.

It is defined only for conservative forces.

ΔU=−W

This means a change in potential energy is negative of work done by the force.

Types of Potential Energy

• Gravitational potential energy

• Elastic potential energy

Mechanical Energy Conservation

Total mechanical energy is the sum of kinetic and potential energy:

E=KE+PE

If no non-conservative force is acting, then:

E=constant

This principle is widely used in solving motion problems.

Equilibrium and Stability

Equilibrium occurs when the net force is zero.

Types of Equilibrium

• Stable Equilibrium: System returns to the original position

• Unstable Equilibrium: System moves away from the position

• Neutral Equilibrium: System stays in the new position

Stability depends on the shape of the potential energy curve.

Important Observations for Exam Preparation

The chapter on Work, Energy, and Power connects multiple areas of physics. It links force, motion, and energy in a clear framework. A strong understanding of formulas and concepts allows solving a wide range of questions.

Here are some key points:

• Work depends on displacement, not path

• Friction always does negative work

• Normal force often does zero work

• Use the work-energy theorem to avoid long calculations

• The area under the graph method is useful for a variable force

• Conservation of energy simplifies many problems

This one-shot coverage builds a structured foundation for NEET 2026 preparation and supports better performance in physics sections.

Regular practice of numerical problems and clarity in sign conventions improve accuracy. Topics like variable force, spring systems, and circular motion require attention but become manageable with repeated revision.