work energy principle

1. WORK ENERGY
PRINCIPLE
BY : SELISH KONJENGBAM, 221024
JASIYA OINAM, 221010
LUSTER PANMEI, 221018
DP TEMUI MARING, 231101L
GROUP NO. 11
DATE: 14/12/23
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2. OVERVIEW
1. WORK ENERGY PRINCIPLE AND ITS EXAMPLES.
2.ENERGY AND ITS TYPES.
3.KINETIC ENERGY, TYPES, EXAMPLES AND ITS CONCEPT.
4.POTENTIAL ENERGY, TYPES, EXAMPLES AND ITS CONCEPT.
5.LINK BETWEEN WORK AND ENERGY.
6.REFERENCE.
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3. WORK ENERGY PRINCIPLE
•It states that an increase in the kinetic energy of a rigid
body is caused by an equal amount of positive work done
on the body by the resultant force acting on that body.
•Conversely, a decrease in kinetic energy is caused by an
equal amount of negative work done by the resultant
force.
•It is given by
𝑊𝑛𝑒𝑡=∆𝐾
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4. EXAMPLES OF WORK ENERGY
PRINCIPLE
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FIG 1.1 POSITIVE WORK:
KICKING A FOOTBALL
FIG 1.2 NEGATIVE WORK:
A ROCKET MOVING UPWARDS

5. FIG 1.3 ZERO WORK:
A MAN PUSHING A WALL
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6. ENERGY
•Energy is a conserved quantity i.e. the capacity of doing
work.
•The law of conservation of energy states that energy can
neither be created nor destroyed but can be transformed
from one form to another.
•It is directionless i.e. it is a scalar quantity.
•The SI unit of energy is Joules.
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7. TYPES OF ENERGY
Kinetic energy Potential energy
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8. KINETIC ENERGY
oKinetic energy of an object is defined as the energy that is
generated due to the motion of an object. It arises when it is
allowed to accelerate the application of some forces on it thus
leading to net work done. Therefore, after the work is done, the
energy is transferred to the objects that lead to the motion of the
object at a constant velocity.
oThe formula for kinetic energy of a point mass m is given by
KE =
1
2
m𝑣2 where, m = mass (kg)
v = velocity (m/s)
KE = kinetic energy (J)
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9. EXAMPLES OF KINETIC
ENERGY
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FIG 2.1 MOVING A BULLET
(TRANSLATIONAL)
FIG 2.2 A ROLLERCOASTER CAR IN DESCENT

10. EXAMPLES OF KINETIC
ENERGY
10
FIG 2.3 A WINDMILL
(ROTATIONAL)
FIG 2.4 A MOVING CAR
( TRANSLATIONAL)

11. FIG 2,4 ATOMS VIBRATING ABOUT THEIR MEAN POSITION
(VIBRATIONAL)
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12. TYPES OF KINETIC ENERGY
Translational kinetic energy:This refers to the energy associated with the linear motion of
an object. It is the most familiar type of kinetic energy.The translational kinetic energy can be
mathematically written as
KE =
1
2
m𝑣2
Rotational kinetic energy: This refers to the energy of an object due to its rotational motion
around an axis. It is also called angular kinetic energy.The rotational kinetic energy can be
mathematically written as
KE =
1
2
𝐼. 𝜔. 𝜔 where I = moment of inertia around the axis of rotation
𝜔 = 𝑎𝑛𝑔𝑢𝑙𝑎𝑟 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
 Vibrational kinetic energy: this refers to the energy of an object due to its vibrational
motion.The vibrational kinetic energy can be mathematically written as
KE =
1
2
k𝑥2 where k = Hooke’s Law constant
 x = displacement from the equilibrium location
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13. CALCULATION OF KINETIC
ENERGY
Let us consider a box of mass m being pushed through a distance d along a
surface by a force, F parallel to that surface.We know that
Work = Force x distance
=>W = F x d
and F = ma
Then,
W = m.a.d { since F = m.a} ------------(i)
From the kinetic equations of motion, it is stated that we could substitute the
acceleration a if the initial and final velocity 𝑣𝑖 and 𝑣𝑓 and the distance is
given.
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So, from that we derive:
𝑣𝑖
2= 𝑣𝑓
2 + 2ad
=> a =
𝑣𝑓
2−𝑣𝑖
2
2𝑑
−−−−−−−−− − ii
Then,
W = m.
𝑣𝑓
2−𝑣𝑖
2
2𝑑
d
= m.
𝑣𝑓
2−𝑣𝑖
2
2
=
1
2
m (𝑣𝑓
2 − 𝑣𝑖
2)
=
1
2
m 𝑣2
The kinetic energy of an object arises from the net work done on it.
Therefore,
KE =
1
2
m 𝑣2
=> 1J =
1
2
.1 kg.(
𝑚
𝑠
)2

15. POTENTIAL ENERGY
• It is the energy possessed by a body due to its position or
condition.
• It is the same as stored energy.
• The formula for potential energy depends on the force acting on
the two objects. It is given by
PE = mgh where m = mass in kg
g = acceleration due to gravity
h = height in meters
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16. EXAMPLES OF POTENTIAL
ENERGY
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FIG 3.1 RIVER WATER AT THE TOP
OF A WATERFALL
( GRAVITATIONAL)
FIG 3.2 AN ARCHER’S BOW WITH THE
STRING PULLED BACK
( ELASTIC)

17. EXAMPLES OF POTENTIAL
ENERGY
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FIG 3.3 EXPLOSIVES
(CHEMICAL)
FIG 3.4 AN INCANDESCENT LIGHT
TURNING OFF
( ELECTRIC)

18. TYPES OF POTENTIAL
ENERGY
• Gravitational potential energy: It is the energy stored in an object as the
result of its vertical position or height.The formula for gravitational potential
energy is mathematically written as
W = mgh
• Elastic potential energy: it is the energy stored in elastic materials as the
result of their stretching or compressing.The more stretch, the more stored
energy.The formula for elastic potential energy is
U =
1
2
k 𝑥2 where U = elastic potential energy
k = spring force constant
• x = string stretched length in m
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o Chemical potential energy: It is the potential energy that
can be absorbed or released during a chemical reaction. It is
mathematically written as
𝜇 = (
𝜕𝐺
𝜕𝑁
) where G = Gibb’s free
energy of the system, N = number of particles.
o Electric potential energy: It is the total potential energy a
unit charge will possess if located at any point in outer space. It
is mathematically written as
U = [
1
(4𝜋𝜀0)
] x [
𝑞1
𝑑
x 𝑞2 ] where 𝑞1, 𝑞2 are two
charges, d = distance.

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o Nuclear potential energy; It is the energy stored in
nuclear bonds.The strong nuclear force holds the nuclear
particles together.The potential energy for certain types of
radioactive decay, such as beta decay, is provided by weak
nuclear forces. It is mathematically written as
E = m 𝑐2 where m = change in mass
c = speed of light
o Magnetic potential energy: It is the form of energy
related not only to the distance between magnetic materials
but also to the orientation or alignment of those materials
within the field. It is given by
U = -𝜇 B where 𝜇 = magnetic moment
B = magnetic field

21. LINK BETWEEN WORK AND
ENERGY
Work and energy are closely related. When we do work to move an object, we
change the object’s energy.We also expand energy to do work. In fact, energy
can be defined as the ability to do work. Energy can take various forms and
one form of energy can transform to the other.
Let us examine how doing work on an object changes the object’s energy. If
we apply force to lift a rock off the ground, we increase the rock’s potential
energy, PE. If we drop the rock, the force of gravity increases the rock’s kinetic
energy as the rock moves downward until it hits the ground.
The force we exert to lift the rock is equal to its weight, w which is equal to its
mass m multiplied by acceleration due to gravity, g.
F = w = mg
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The work we do on the rock equals the force we exert multiplied by the
distance, d that we lift the rock.The work we do on the rock’s gain in
gravitational potential energy, PE.
W = PE = mgd
Kinetic energy depends on the mass of an object and its velocity, v.
KE =
1
2
m 𝑣2
When we drop the rock the force of gravity causes the rock to fall,
giving the rock kinetic energy, then the net work equals the change in
the value of the quantity
1
2
m 𝑣2. This is the statement of the work-
energy theorem, which is mathematically expressed as
W = ∆𝐾𝐸
=
1
2
m 𝑣2
2 −
1
2
m 𝑣1
2
The subscripts 2 and 1 indicate the final and initial velocity, respectively.
This theorem was proposed and successfully tested by James Joule.

23. CONCLUSION
•The work energy theorem allows us to combine our
understanding of work and kinetic energy.
•When work is done on an object, the force exerted on an
object causes a displacement.
•Since kinetic energy is the energy of a motion, the force
is also changing the object’s kinetic energy as it causes
movement.
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24. REFERENCE
1. https://openstax.org/books/physics/pages/9-1-work-power-and-the-work-
energy-theorem
2. https://studiousguy.com/potential-energy-examples/
3. https://www.yourdictionary.com/articles/examples-potential-energy
4. https://en.wikipedia.org/wiki/Potential_energy
5. https://byjus.com/question-answer/what-are-i-translational-ii-rotational-
and-iii-vibrational-kinetic-energies-give-at-least-one/
6. https://www.physics-and-radio-electronics.com/physics/energy/kinetic-
energy/forms-of-kinetic-energy.html
7. https://studiousguy.com/examples-of-kinetic-energy-in-everyday-life/
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THANK YOU
FOR YOUR ATTENTION !
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