Understanding Different Types of Energy and Their Applications - Prof. Brian N. Espino, Study notes of Physics

Download Understanding Different Types of Energy and Their Applications - Prof. Brian N. Espino and more Study notes Physics in PDF only on Docsity! Ch. 6 Energy Energy is possibly the most important physics concept. The ability to harness or make use of energy by people has always driven civilization. Simplest , most common case of energy consumption is eating. You obtain chemical energy from the food that your body stores. When you move around, you then use up that energy. Forms of energy fossil fuels – coal, oil, gas, chemically decomposed remains of biological material (has carbon) These are examples of sources of chemical energy. chemical energy – comes from the molecular structure of the material Burning methane CH4 + 4O2 = CO2 + 2H2O + excess thermal energy When we rearranged the atoms in the molecules, energy was released. kinetic energy – energy that is due to motion Whenever something is moving, this is kinetic energy. K = ½ m v2 Any motion that results in kinetic energy. It can be the motion of a hockey puck sliding on the ice. (translational motion) A spinning wheel (rotational motion) A ball rolling down a hill is a combination. The ball translates and rotates. gravitational energy – also called gravitational potential energy – comes from gravitational forces. For objects on/near the Earth, this energy is produced from the gravitational attraction to the Earth. When an object is raised or lower in elevation, it gains or loses gravitational energy. gravitational energy = m g h, = weight x height When you climb up a mountain, you increase your gravitational energy As the temperature increases, the particles move faster and faster. Temperature is really a measurement of the average velocity of the individual particles. The energy the particles have due to this microscopic motion is the thermal motion. Thermal energy is similar to microscopic kinetic energy. Or kinetic energy is macroscopic thermal energy, we can observe it easily on the large scale. electromagnetic energy – combination of electric energy and magnetic energy. This has to do with electric charges and magnets. We will talk about this later. radiant energy – the energy in light beams. Energy that is carried by light that is used to warm objects. This gets transferred to thermal energy for practical use. Sunlight is a common example of radiant energy. Earlier we saw that chemical energy results from the molecular structure of material. Nuclear energy – comes from the nuclear structure. The way that protons and neutrons are arranged in the nucleus. When a nuclear reaction takes place, energy is released. We will cover this later. examples where no work is done People leaning on a immovable wall - no work is done, even though there is a force Waiter carrying a plate from underneath - no work is done, force and motion are perpendicular Magnetic field exerts a force on a moving charged particle. Makes is orbit in a circle. - no work is done, force and motion are perpendicular Holding a weight still, over your head - no work, there’s no motion examples where there is work letting a ball drop - the weight is in the direction of the motion (down) A truck towing a trailer - truck exerts force on trailer in direction of motion An electric field accelerating a charged particle - the field exerts a force in the direction the particle moves Friction produces negative work on a sliding object. The work is negative because the force is opposite to the direction of motion. Work When there is a net work (none zero) done on an object, the object will change speeds. Pretend you are on the bank of a frozen pond where a sled is on the ice. There is a rope tied to the sled that you can pull on. When you pull on the rope, the sled speeds up towards you. You did work on the sled. Conclusion: • Positive work will speed up an object. • Negative work will slow it down. • Remember kinetic energy. Kinetic energy was energy due to motion and depended on the speed of an object. KE = ½ m v2 • When you do work on an object, you change the kinetic energy. Conservation of Energy • The total energy of all the participants in a process will stay constant. • Energy cannot be created or destroyed. • Energy merely is transferred from one form to another. • Conservation of energy example • A boulder is on the edge of a cliff sitting still. The boulder has gravitational potential energy because it is at a higher level than the ground. If the boulder falls off the edge that potential energy is converted to kinetic energy as it falls. • As the boulder falls it loses gravitational potential energy but gains kinetic energy as it speeds up. power = the rate at which work is done power = work/time remember when you do work you change the kinetic energy. power = KE/time SI units of power is the Watt 1 W = 1 J/s other unit horsepower 1 hp = 746 W kilowatt-hour is a unit of energy power x time = energy work = force x distance power = work / time force x distance / time = force x velocity It takes more power to exert a force quickly. Power Power is related to how fast a force can be applied. Picking up a heavy weight slowly may not require much power. Picking up the same weight quickly will require more power. Weightlifting examples: compare the power required to perform a bench press and an Olympic snatch.