a

1. Conserv
ationof
Energ
y

2. 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.

3. Conservation of Energy
Energy AND Conservation of Energy

4. 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!

5. Conservation of Energy
Conservation of Energy
Potential Energy
(joules) p
E = mgh
Potential 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.
Mass (kg)
Height (m)
Acceleration of
gravity (m/sec2)

6. Conservation of Energy
Conservation of Energy
Ek = 1 mv2
2
Kinetic 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:
Mass (kg)
Speed (m/sec)
Kinetic
Energy
(joules)

7. 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

8. Problem:

9. Problem:

11. Conservation Of Energy
A ball with mass of 2kg is dropped
from the top of a building that is 30m
high. What is the approximate
velocity of the ball when it is 10m
above the ground?

12. A ball with mass of 2kg is dropped from the top of a
building that is 30m high. What is the approximate velocity
of the ball when it is 10m above the ground?
So 400 Joules are converted from gravitational potential to kinetic
energy, allowing us to solve for the velocity, v.

13. A pendulum with a mass of
405kg reaches a maximum
height of 2.4m. What is its
velocity at the bottommost
point in its path?

16. We can cancel the mass from each term and
plug in the given values to solve for the
velocity at a height of 7m.