Do Now 5/7

1. Do Now 5/7 1) Why does air pressure decrease from the troposphere to the exosphere? a) because there are fewer air molecules as altitude increases b) because there are more air molecules as altitude increases c) because there are higher temperatures as altitude increases d) because there are lower temperatures as altitude increases 2) How does the temperature of the stratosphere compare to the mesosphere? a) It is colder than the mesosphere because the stratosphere contains the ozone layer. b) It is warmer than the mesosphere because the stratosphere contains the ozone layer. c) It is colder than the mesosphere because the stratosphere contains the ionosphere. d) It is warmer than the mesosphere because the stratosphere contains the ionosphere.

2. Energy

3. What is it? • “the ability to do work” • The combination of energy and matter make up the universe: • Matter is substance, and energy is the mover of substance.

4. Nature of Energy • You use energy when: • You hit a baseball • Throw a runner out at 1st base • Run the 100m dash • Leap for the long jump

5. Nature of Energy Living organisms need energy for growth and movement

6. The Law of Conservation of Energy • Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

7. Energy and its Divisions • Potential Kinetic Chemical Gravitational Elastic

8. energy of position or energy in storage. Water behind a dam Hammer over head Food on the plate energy of motion, the form capable of doing work Flowing water A falling hammer Electrons regenerating ATP in a bio’l cell PotentialKinetic

9. What is Potential Energy? • An object can store energy as the result of its position. • Think of a wrecking ball or a drawn bow.

10. Gravitational Potential Energy • Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. • The energy is stored as the result of the gravitational attraction of the Earth for the object. (Think of the wrecking ball)

11. Gravitational Potential Energy • Dependent on two variables; height and mass • More massive objects have greater gravitational potential energy. • The higher that an object is elevated, the greater the gravitational potential energy. • PE = (Mass) (accel due to Gravity) (Height)

12. Do Now 5/8 1. How does the convection of air produce thunderstorms? A) by causing warm air to sink and cold air to rise B) by causing warm air to rise and cold air to sink C) by causing both warm air and cold air to rise D) by causing both warm air and cold air to sink 2. The cell membrane is unable to work properly. How could this affect plant and animal cells? A It could affect their ability to absorb sunlight. B It could affect their ability to make proteins. C It could affect their ability to store water. D It could affect their ability to remove waste.

13. Gravitational Potential Energy • Dependent on two variables; height and mass • More massive objects have greater gravitational potential energy. • The higher that an object is elevated, the greater the gravitational potential energy. • PE = (Mass) (accel due to Gravity) (Height)

14. Gravitational Constant • The gravitational constant, g, is the acceleration of an object due to gravity. This acceleration is about 9.8 meters per second on earth.

15. Harder Problems for PE • A 12 kg cat who is resting on a tree has a potential energy of 50 J. Calculate its position (height) relative to the ground. • A girl runs up a 5 meter high flight of stairs and she has 1000 J of potential energy at the top. Calculate her mass.

16. Elastic Potential Energy • Potential energy due compression or expansion of an elastic object. • The amount of elastic potential energy stored in such a device is related to the amount of stretch of the device - the more stretch, the more stored energy. • http://www.youtube.com/watch?v=Jnj8mc04r9E

17. Chemical Potential Energy • Potential energy stored within the chemical bonds of an object • It is the energy that can be emitted when the bonds are broken.

18. Kinetic Energy • Roller coasters work because of the energy that is built into the system. Initially, the cars are pulled mechanically up the tallest hill, giving them a great deal of potential energy. From that point, the conversion between potential and kinetic energy powers the cars throughout the entire ride. http://www.youtube.com/watch?v=SmVsD8QLsgk

19. Kinetic Energy Equation • KE depends upon two variables: the mass (m) of the object and the speed (v) of the object. • Equation - - KE = 0.5 • m • v2

20. A Few Examples • 1. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s. • 2. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy?

21. Continued but more difficult • 3. Missy Diwater, the former platform diver for the Ringling Brother's Circus, had a kinetic energy of 12 000 J just prior to hitting the bucket of water. If Missy's mass is 40 kg, then what is her speed?

22. What to expect • Describing Motion • Vocabulary Terms gone over • Calculating speed and average speed • Graphing D/T and V/T graphs • The difference between the lines on a graph • How to find slope and creating graph scenarios • The differences between energy and its forms • Equations involving PE and KE, must know formulas • Law of Conservation of Energy and what it states