PotentialPotential andand

KineticKinetic EnergyEnergy

Prepared and Presented By – ( IX-Prepared and Presented By – ( IX-B ) B ) 1} Yash1} Yash - 11 - 112} Priyank - 62} Priyank - 6

How is Energy divided? How is Energy divided?

PotentialEnergy

KineticEnergy

EnergyEnergy

GravitationPotentialEnergy

ElasticPotentialEnergy

ChemicalPotentialEnergy

What is Kinetic Energy?What is Kinetic Energy?

o Energy acquires the object due to its Energy acquires the object due to its motion.motion.

o K.E. = .5(mass x speedK.E. = .5(mass x speed22))

Derivation of Kinetic energy Derivation of Kinetic energy formula formula

Where there are no opposing forces, a moving body needs noforce to Where there are no opposing forces, a moving body needs noforce to keep it moving with a steady velocity If, however, a resultant force keep it moving with a steady velocity If, however, a resultant force does act on a moving body in the direction of its motion, then it will does act on a moving body in the direction of its motion, then it will accelerate and the work done by the force will become converted into accelerate and the work done by the force will become converted into increased kinetic energy in the body.increased kinetic energy in the body.

    In order to calculate the kinetic energy of a body of massIn order to calculate the kinetic energy of a body of mass m m moving  moving with velocity with velocity vv,we begin by supposing that the body starts from rest ,we begin by supposing that the body starts from rest and is acted upon by a force and is acted upon by a force F F ( no friction or other forces acting ).( no friction or other forces acting ).

  This force will give the body a uniform acceleration   This force will give the body a uniform acceleration aa, and will , and will acquire a final velocity acquire a final velocity vv, after travelling a distance , after travelling a distance xx. These . These quantities, a,v and x will be related by the equation quantities, a,v and x will be related by the equation                                                       vv² = ² = uu² + 2 ² + 2 axax     In accordance with the law of conservation of energy, the work    In accordance with the law of conservation of energy, the work done by the force done by the force FF in pushing the body through distance in pushing the body through distance x x will  will become converted intobecome converted intokinetic energykinetic energy of motion in the body. of motion in the body.

Thus,Thus,

                                                                                                                                                

                                                       

therefore, substituting for therefore, substituting for FF,                  ,                                                                      work done = ma × s.......................( 1 )work done = ma × s.......................( 1 )

Applying the equation   Applying the equation   v² = u²v² = u² + 2  + 2 asas and remembering that  and remembering that u = 0u = 0                                                                         v² = 0 + 2 as v² = 0 + 2 as                       a =   v² / 2s                        a =   v² / 2s   

                                                                substituting this value of substituting this value of aa in equation ( 1 ), we obtain, in equation ( 1 ), we obtain,

  work done = m × v² / 2a × s = kinetic energywork done = m × v² / 2a × s = kinetic energyor or kinetic energy ( k.e.) kinetic energy ( k.e.) = 1/2  = 1/2  m/v²m/v²  

  

This expression, 1/2  This expression, 1/2  m  vm  v², gives the energy in joules or ergs according to the ², gives the energy in joules or ergs according to the system of units used.system of units used.

work done = force × distance                    = F × s but, F = ma

Example of Kinetic EnergyExample of Kinetic Energy

A man surfing on the slops filled A man surfing on the slops filled with ice with the help of with ice with the help of resultant kinetic energy.resultant kinetic energy.

What is Potential Energy?What is Potential Energy?

o Energy that is stored and waiting Energy that is stored and waiting to be used later.to be used later.

Example of Potential EnergyExample of Potential Energy

A child playing with A child playing with elastic ball elastic ball attached with a attached with a racket which stores racket which stores energy when it energy when it gets stretched.gets stretched.

Conversion of Potential Conversion of Potential energy in Kinetic Energyenergy in Kinetic Energy

Potential energy is the energy stored within a physical Potential energy is the energy stored within a physical system as a result of the position or configuration of the system as a result of the position or configuration of the different parts of that system. It has the potential to be different parts of that system. It has the potential to be converted into other forms of energy such as kinetic converted into other forms of energy such as kinetic energy and to do work in the process. energy and to do work in the process.

Conversion of Potential Conversion of Potential energy in Kinetic Energyenergy in Kinetic Energy

Potential energy is energy waiting to happen.Potential Potential energy is energy waiting to happen.Potential energy is when the object (such as the car on the roller energy is when the object (such as the car on the roller coaster) is stopped and/ or not moving.Kinetic energy is coaster) is stopped and/ or not moving.Kinetic energy is energy in motion. So to make potential energy kinetic, energy in motion. So to make potential energy kinetic, you put the object in motion.you put the object in motion.