Presentation Transcript

1. 15.1 Energy and It’s Forms Energy – The ability to do work. Energy is measured in Joules.  W = F x d Energy = F x d Work is the transfer of energy. A The sun gives off energy in the form of heat and light. B Plants convert sunlight into food that we can process and eat. C People convert food energy into muscle movement
2. Types of Energy Kinetic Energy- Energy of motion. KE = ½ mv2 When the mass is doubled, the KE is doubled. When the velocity is doubled, the KE is quadrupled.
3. Kinetic Energy Math Practice 1.A 70.0-kilogram man is walking at a speed of 2.0 m/s. What is his kinetic energy? 2.A 1400-kilogram car is moving at a speed of 25 m/s. How much kinetic energy does the car have? 3.A 50.0-kilogram cheetah has a kinetic energy of 18,000 J. How fast is the cheetah running? (Hint: Rearrange the equation to solve for v.)
4. Types of Energy Potential Energy – Energy stored as a result of position or shape. PE becomes KE when the object starts moving. There are two types of potential energy. Gravitational Potential Energy- GPE depends on the height of an object. It increases as the object is raised. GPE = mgh (g = 9.8m/s2) Elastic Potential Energy- EPE is the potential energy of an object that is stretched or compressed (springs) This diver has gravitational potential energy as she stands at the end of a diving board.
5. Forms of Energy There are 6 major forms of energy. 1. Mechanical Energy- The energy associated with the motion and position of everyday objects. ME is NOT limited to machines. ME = KE + PE EX: speeding trains 2. Thermal Energy – The total PE and KE of all the microscopic particles in an object. When an object’s atoms move faster, its thermal energy increases and the object becomes warmer.
6. Forms of Energy 3. Chemical Energy- Energy stored in the chemical bonds of a compound. When the bonds are broken, the released energy can do work. EX: burning wood This family is using the chemical energy of burning wood to produce thermal energy for heating marshmallows
7. Forms of Energy 4. Electrical Energy- energy associated with electric charges. EX: lightning, CD players 5. Electromagnetic Energy- A form of energy that travels through space in the form of waves EX: visible light and X-rays A Lightning bolts transfer electric charge. B Galaxies are giant structures in space that typically contain billions of stars. The stars give off enormous amounts of electromagnetic energy
8. Forms of Energy 6. Nuclear Energy- The energy stored in the atomic nuclei of an atom. EX: nuclear fission - a process that releases energy by splitting nuclei apart Ex: nuclear fusion, releases energy when less massive nuclei combine to form a more massive nucleus
9. 15.2 Energy Conversion and Conservation Energy Conversion Energy can be converted from one form to another form. When energy changes forms, the total energy remains unchanged. Energy is converted from one form to another as this match is lit.
10. Conservation of Energy The Law of Conservation of Energy - The law of conservation of energy states that energy cannot be created or destroyed. In a closed system, the amount of energy present at the beginning of a process is the same as the amount of energy at the end. Gravitational potential energy is converted to kinetic energy as the object falls. Some gulls use energy conversion to obtain food by dropping oysters onto rocks.
11. Energy Conversion Calculations Conservation of Mechanical Energy (KE+PE)beginning = (KE+PE)end A 10-kg rock is dropped and hits the ground below at a speed of 60 m/s. Calculate the gravitational potential energy of the ball before it was dropped. You can ignore the effects of friction. 2.A diver with a mass of 70.0 kg stands motionless at the top of a 3.0-m-high diving platform. Calculate his potential energy relative to the water surface while standing on the platform, and his speed when he enters the pool. (Hint: Assume the diver's initial vertical speed after diving is zero.) 3.A pendulum with a 1.0-kg weight is set in motion from a position 0.04 m above the lowest point on the path of the weight. What is the kinetic energy of the pendulum at the lowest point? (Hint: Assume there is no friction.)
12. Energy and Mass Einstein’s theory of relativity E = mc2 E = energy m = mass c = speed of light Energy and mass are equivalent and can be converted into each other. Energy is released as matter is destroyed, and matter can be created from energy. The speed of light is a very large number, 3 x 108 m/s, and it is squared. Sooo….
13. Energy and Mass A tiny amount of matter can produce an enormous amount of energy 1 g of matter = 9 x 1013 J of energy 1 g of TNT = 2931 J of energy  In nuclear fission (splitting atoms) and nuclear fusion (creating atoms), large amounts of energy are produced from very small amounts of matter.  The law of conservation of energy has been modified to include mass and energy are conserved together.