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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 1

2. OVERVIEW WORK ENERGY PRINCIPLE AND ITS EXAMPLES. ENERGY AND ITS TYPES. KINETIC ENERGY, TYPES, EXAMPLES AND ITS CONCEPT. POTENTIAL ENERGY, TYPES, EXAMPLES AND ITS CONCEPT. LINK BETWEEN WORK AND ENERGY. REFERENCE. 2

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 =   3

4. EXAMPLES OF WORK ENERGY PRINCIPLE 4 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 5

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. 6

7. TYPES OF ENERGY Kinetic energy Potential energy 7

8. KINETIC ENERGY Kinetic 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. The formula for kinetic energy of a point mass m is given by KE = m where, m = mass (kg) v = velocity (m/s) KE = kinetic energy (J)   8

9. EXAMPLES OF KINETIC ENERGY 9 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) 11

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 = m 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 = where I = moment of inertia around the axis of rotation 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 = where k = Hooke’s Law constant x = displacement from the equilibrium location   12

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 and and the distance is given.   13

14. 14 So , from that we derive: = + 2ad => a = Then, W = m. d = m. = m ( ) = m The kinetic energy of an object arises from the net work done on it. Therefore, KE = m => 1J = .1 kg.  

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 15

16. EXAMPLES OF POTENTIAL ENERGY 16 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 17 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 = k where U = elastic potential energy k = spring force constant x = string stretched length in m   18

19. 19 Chemical potential energy : It is the potential energy that can be absorbed or released during a chemical reaction. It is mathematically written as ) where G = Gibb’s free energy of the system, N = number of particles. 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 = [ ] x [ ] where , are two charges, d = distance .  

20. 20 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 where m = change in mass c = speed of light 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 = - B where = 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 21

22. 22 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 = m 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 m is the statement of the work-energy theorem, which is mathematically expressed as W = = m m 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. 23

24. REFERENCE https://openstax.org/books/physics/pages/9-1-work-power-and-the-work-energy-theorem https://studiousguy.com/potential-energy-examples/ https://www.yourdictionary.com/articles/examples-potential-energy https://en.wikipedia.org/wiki/Potential_energy https://byjus.com/question-answer/what-are-i-translational-ii-rotational-and-iii-vibrational-kinetic-energies-give-at-least-one/ https://www.physics-and-radio-electronics.com/physics/energy/kinetic-energy/forms-of-kinetic-energy.html https://studiousguy.com/examples-of-kinetic-energy-in-everyday-life/ 24

25. 25 THANK YOU FOR YOUR ATTENTION ! ANY QUESTIONS