Understanding Energy: Kinetic, Potential, and Transformations
Understanding Energy
1. How do you define energy? It is the ability to produce work.
Main Forms of Energy
2. Main forms of energy: heat, light, electrical, chemical, atomic, mechanics.
Mechanical Energy
3. What is mechanical energy? It is a form of energy that corresponds to work produced by a force of mechanical origin.
4. There are two kinds of mechanical energy: kinetic and potential.
Kinetic Energy
5. A body in motion has kinetic energy.
6. The value of the kinetic energy of a body is equal to half the product of its mass by the square of its velocity:
Ec = ½ m * V2 and is measured in KPM (kilopondímetros).
7. A car of mass 750kg flowing at a speed of 60 km/h collides with an obstacle. What kinetic energy is developed?
m = 750 kg
v = 60 km/h = (60 * 1000) / 3600 = 60000 / 3600 = 16.67 m/sec
KE = ½ m * V2 kpm (m/sec)
Ec = (750 / 2) * 16.672 = 375 * 277.88 = 104,205 kpm
Potential Energy
8. The potential energy of a body depends on: body weight and height to which they are situated.
9. A body of 50-lb weight is suspended 30 meters above the ground. What potential energy does it have?
Ep = P * h = 50 * 30 = 1,500 kpm
Energy Sources
10. The main natural sources of energy include muscle, water, air, fuel, and the Sun.
11. All natural energy sources come from some form of the Sun.
12. Artificial energy sources are those produced by man.
Energy Transformation and Conservation
13. Energy can be transformed from one form to another.
14. The law of conservation of energy says that energy is neither created nor destroyed, only transformed.
15. Kinetic energy can become potential and potential kinetic.
16. In any energy conversion, the amount of initial energy is not exactly equal to the amount of energy output, since there is always a kind of energy which is transformed into heat.
17. The performance of a machine is equal to the ratio of useful work and work motor.
18. Nuclear energy is released into the break at the core of an atom.
19. Energy is the ability to produce work.
20. An example of mechanical energy: The energy that we have to run on a bicycle (potential energy) and do some travel (mechanical energy).
21. Case studies illustrating kinetic and potential energy: The energy we have to ride a bicycle (potential energy) and do some travel (mechanical energy), or water from a waterfall (potential energy), but fell to move the blades of a turbine (mechanical energy).
22. The sum of kinetic and potential energy of a body is constant.
23. Energy sources can be natural or artificial.
24. The potential energy of a body is equal to its weight by the height at which it is.
25. The energy a body possesses by virtue of its position in space is called potential.
26. The kinetic energy of a body is equal to half the product of its mass by the square of its velocity.
27. The energy possessed by a body in motion is called kinetic energy.
28. Kinetic and potential energy are two aspects of mechanical energy.
29. Heat has the capacity to produce work. Electricity is a form of energy. The conversion of gasoline produces gases and heat to chemical energy.
Energy Transformations: Case Studies
30. Energy Transformations Case Studies:
- Electric radiator: electric to heat
- Heat into mechanical: steam
- Mechanics in hydroelectric: power
- Electric light: fluorescent tube
Problems
1. What work does a person who moves a table 0.02 km applying a force of 2 Newtons? 0.02 km * 1000 = 20m
T = F * d
T = 2 * 20
T = 40 Joules
2. What work will be needed to make a shift from applying a 2000dm force of 4 Newtons? 2000dm: 10 = 200m
T = F * d
T = 4 * 200 = 800 Joules
3. What kinetic energy develops a stone weighing 2 km, if launched at a speed of 10m/seg? 2 km * 1000 = 2000m
KE = ½ m * V2
(2000 / 2) = 1000 kpm
1000 kpm * 9.8 = 9800 Joules
4. A body that weighs 30 lb and is at a height of 50m. What will be your energy potential?
Ep = P * h
Ep = 30 * 50
Ep = 1500 kpm
1500 * 9.8 = 14700 Joules
5. How much work will make a stone that weighs 12 kg if it has a velocity of 100m/seg?
KE = ½ m * V2
(12 / 2) = 6 kpm
6 kpm * 10000 = 60000
60000 * 9.8 = 588000 Joules
6. What potential energy has a lamp that weighs 15 lb and is at a height of 4m?
Ep = P * h
Ep = 15 * 4 = 60 kpm
60 * 9.8 = 588 Joules