Work done on an object is defined as the magnitude of the force multiplied by the distance moved by the object in the direction of the applied force.
Work done = force × distance
= F × s
1 Joule = 1 Newton × 1 metre.
The unit of work is joule.
- When both the force and the displacement are in the same direction, positive work is done.
- When force acts in a direction opposite to the direction of displacement, the work done is negative.
The energy of a body is its capacity of doing work. The S. I. unit of energy is Joule (1 KJ = 1000 J).
Forms of Energy
There are many forms of energy, such as kinetic energy, potential energy, etc.
Law of Conservation of Energy
Energy cannot be created and cannot be destroyed. We can only change the form of energy. This law is called the Law of Conservation of Energy.
Kinetic energy is the energy possessed by a moving body by virtue of its motion.
m= Mass of object
v= Speed of object
Potential energy is the energy possessed by the body due to its position or shape. It is also referred as stored energy.
Potential energy(P.E) = mgh
GRAVITATIONAL POTENTIAL ENERGY
It is the energy possessed by a body due to its position above ground. The general form of gravitational potential energy is
P.E. = − GMm/r,
where M and m refer to the masses of the two bodies being separated;
r is the distance between the centers of the masses.
ELASTIC POTENTIAL ENERGY
It is the energy stored in a spring. The magnitude of the force required to stretch a spring is given by
F = − kx,
where x is the distance of stretch (or compression) of a spring from the unstressed position,
k is the spring constant.
It is defined as the sum of kinetic and potential energy.
COMMERCIAL UNIT OF ENERGY
Since joule is very small, thus, large quantity of energy is expressed in kilo watt hour and is written as kWh. KWh is the commercial unit of energy.
1 unit = 1 kWh
1 kWh is the energy consumed by a device of power 1 kW in 1 hour.
1 kWh = ( 1 kW)(1 hr)
= 3600,000 J
|For Bank Exams||@999 or @1,199|
|For SSC Exams||@599|
|For Insurance Exams||@499|
|For Teaching Exams||@399|