# Work

## Work

• Work is a fundamental concept in physics dealing with energy transfer.
• Defined as the product of the force applied to an object and the distance moved by the object in the direction of the force. Expressed mathematically as Work (W) = Force (F) * Distance (d).
• It has the unit of Joules (J) in the International System of Units (SI). It’s important to remember that 1 Joule equals 1 Newton metre (Nm).
• Work is considered to be done on an object when the force applied causes displacement of the object.
• It is considered positive when force and displacement are in the same direction; conversely, work is considered negative when force and displacement are in opposite directions.
• Work is a scalar quantity, as it has magnitude but no direction. If an object moves in a circular path, the total work done is zero, because the force and displacement are perpendicular to each other.
• Kinetic energy of an object increases when work is done on the object, and it decreases when work is done by the object. This is the basis of the work-energy theorem.

## Principle of Work and Energy

• The total work done on a particle is equal to the change in its kinetic energy.
• Takes into account not only the work done by the external forces but also by the internal forces.
• Useful in solving problems involving work and energy, for example, finding the work done for an object to reach a certain velocity or the velocity of an object after a certain amount of work is done on it.

## Work done by Variable Forces

• If the force acting on an object is not constant, we integrate to find the work done.
• The principle of integration can also be used when the force depends on the position of the objects in their path of motion.
• Integration allows for the calculation of work done by varying forces across distances.

## Conservation of Mechanical Energy

• The total mechanical energy (potential energy plus kinetic energy) of an isolated system, subject to conservative forces, remains constant.
• Conservation of energy plays a critical role in work and energy problems.

## Power

• Power is the rate at which work is done, which is the amount of work per unit time.
• Power has the unit Watts (W) in the International System of Units (SI), i.e., 1 Watt equals 1 Joule per second (J/s).
• Power is also considered when discussing the efficiency or efficacy of work done by a system or machine.

Remember, a sound understanding of these concepts is essential to effectively answer questions on work, energy and power. These should be combined with rigorous practice for thorough preparation.