Conservation Of Energy
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Transcript of Conservation Of Energy
Energy AND Conservation of Energy
Energy is the ability to make things change.
A system that has energy has the ability to do work.
Energy is measured in the same units as work because energy is transferred during the action of work.
Conservation of EnergyEnergy AND Conservation of Energy
The Law of Conservation of Energy
Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.
Law of Conservation of Energy
P.E K.E. P.E. K.E. … Is energy lost?
No Energy is converted!
Conservation of Energy
Potential Energy
Conservation of Energy
Potential energy exists whenever an object which has mass has a position within a force field. The most everyday example of this is the position of objects in the earth's gravitational field.
Potential Energy (joules) Ep = mgh
Mass (kg)
Height (m)
Acceleration of gravity (m/sec2)
Conservation of Energy
Kinetic Energy:
Conservation of Energy
Kinetic Energy exists whenever an object which has mass is in motion with some velocity. Everything you see moving about has kinetic energy. The kinetic energy of an object in this case is given by the relation:
Ek = 1 mv2
2
Speed (m/sec)
Mass (kg)
Kinetic Energy (joules)
Conservation of Energy
Prove The Conservation of Energy:- Now prove that the Conservation law holds good in the case of a
freely falling body.
• Let a body of mass 'm' placed at a height 'h' above the ground, start falling down from rest.
• In this case we have to show that the total energy (potential energy + kinetic energy) of the body at A, B and C remains constant i.e, potential energy is completely transformed into kinetic energy.
Law of Conservation of Energy
Conservation of Energy
At A :-
Potential energy = mgh
Kinetic energy = 0
[the velocity is zero as the object is initially at rest]
Total energy at A = P.E. + K.E.
Total energy at A = mgh ………….. …(i)
At B :-
P. Energy = mgh
= mg(h - x) [Height from the ground is (h - x)]
PE = mgh - mgx
Kinetic energy The body covers the distance x with a velocity v.
we know that v2 - u2 = 2aS …………. Here, u = 0, a = g and S = x
K. Energy = mgx
Total energy at B = P.E. + K.E.
Total energy at B = mgh……………………(ii)
Law of Conservation of Energy
Conservation of Energy
At C :-
Potential energy = m x g x 0 (h = 0)
P. Energy = 0
For Kinetic energy
The body covers the distance h with a velocity v.
We know that v2 - u2 = 2aS Here, u = 0, a = g and S = h
Kinetic Energy = mgh
Total energy at C = P.E. + K.E.
Total energy at C = mgh ………………. …(iii)
From equations (i), (ii) and (iii)
That the total energy of the body remains constant at every point.
Thus,
We conclude that Law of Conservation Of Energy
Holds good in the case of a freely falling body
.
Law of Conservation of Energy
