Work power & energy

Mechanical Engineering

Work power & energy:

Work: Work is said to be done if we apply force on a body and the body moves in the direction of force applied. The work can be calculated by the product of the force and the distance through which a body moves.

i.e.                               Work done = Force (F) X distance (d)

The work done is expressed in joule. Which is defined as the work done when a force of 1 newton is applied on a body through a distance of 1 metre?

Power: The rate of doing work is known as power.

i.e.                               Power = Work done/Time taken

The power is expressed in joule/sec. or watt     (1 watt = 1 Newton metre/second)

The bigger unit of power such as Horse power and Kilowatt are also used. Where 1 Horse power = 746 watts and 1 Kilowatt = 1000 watts.

Energy: Capacity to do work is called energy. It has the same unit as that of work i.e. joule. It can also be expressed in calories.

 1 Calorie = 4.18 joules

The energy can be in transition or is stored in the system boundaries.

Examples of energy stored in the system are

  1. Potential energy
  2. Kinetic energy
  3. Internal energy

Potential energy (PE): The energy of a body by virtue of its height is known as potential energy.

PE = mgh

Where m is the mass of body, g is gravitational acceleration and h is the height through which body is lifted.

Kinetic energy (KE): The kinetic of a body by virtue of its velocity is known as Kinetic energy.

KE = ½ mv2

Where m is the mass of the body and v is the velocity with which it is moving.

Internal Energy: The balance energy is known as the internal energy.

Heat and work are the forms of energy in transition.