Rollercoaster Physics: Energy

Transcription

1 Physics Regular 1112 Williams Rollercoaster Physics: Energy Packet -1 / Chapter 6

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3 Name: No:: Conservation of Energy The Mechanical Universe Video Guide 1. Although energy can change forms, the total amount of energy in the Universe is. 2. The Teacher in the beginning of the video mentions an energy crisis. What evidence is there that we are still in an energy crisis today? 3. Name three sources of energy currently used in out society? 4. We know work as Work = Force * Distance. The video relates gravitational potential energy to the work done with respect to gravity. What was the equation given to describe this relationship? 5. What is the constant force of gravity? (Hint: your answer should be an equation.) 6. What is the equation for calculating gravitational potential energy? 7. When the weightlifter lifts the weight, where is the potential energy stored? 8. Exercise machines use cams, pulleys and levers and inclined planes to do the same thing to the weights. What are they doing to the weights? (Hint: The video uses U to represent PE)

4 9. When potential energy is released, what does it transform into? 1. The video uses advanced math steps to derive an equation to find the kinetic energy of a moving object. What is this equation? 11. A pole-vaulter runs to the make as fast as they can until they reach the line and then they use the pole to convert their kinetic energy into, raising them high above the ground by doing work on the pole. 12. Explain different types of energy the ball has at the left, middle, and right of the diagram. 13. What contribution did Joule make to the understanding of conservation of energy? 14. The energy that is lost in a system is transformed into what? 15. What is the unit of energy? CHALLENGE: What is the term used to describe the continuing dissipation of energy in the form of heat? Name No

5 Kinetic and Potential Energy Skate Park Lab Objective: The objective of this lab is to observe the conservational laws of energy, Materials: Computer, internet, paper and pencil. Procedure: Name No Part 1 1. Log into the computers and go to In the left hand column, find motions and click on it. Run Energy Skate Park. 2. Take 5 min to familiarize yourselves with the software. Be sure to try changing the environmental parameters on the right menu. 3. Mimic Tony Hawk on the half pipe with your character and his environment. Be sure to have a flat section in the middle on the ground level and to make the two lips of the pipe perpendicular to the ground so that you don t lose your skater. 4. Push and put the friction slider to a coefficient of. Move the skater to an inch or two above the lip of the half pipe and push. Q1: What do you notice about the height of the skater at the top of each lip? Q2: When the skater s vertical velocity is, his potential energy is at a max and his kinetic energy is. What is the equation for the skater s potential energy at this point? Q3: When the skater is at the bottom of the ramp, on the flat portion, his kinetic energy is at a max and his potential energy is. What is the equation for the skater s kinetic energy? Q4: What is the relationship between the PE max and KE max? 5. Pause the simulation and bring the skater back over the lip of the ramp. Increase the coefficient of friction to.12 and push. Observe the height of the skater each time he comes off the lip of the ramp. Q5: What do you notice about the height of the skater each time he reaches his maximum height? 6. Pause the simulation and put the skater back over a lip of the ramp. Open up the bar graph and again release the skater but with friction this time. You may have to change the mass of the skater in order to decrease the energy levels so that they do not go off the screen. Q6: The creators of this applet missed an important piece of this graph. They did not label the y-axis. What is the unit we measure energy in that should have been used to label the axis?

6 Q7: As the skater goes too and fro you will see the energy translate back and forth between KE and PE, but overall you will notice a decrease in the energy as the skater slows down. According to the graph, where does the energy go? 7. After the skater has come to a stop you will notice that the potential energy does not reach at the bottom of the ramp. That is because there is potential energy stored in the mass of all objects, but that is a topic to be discussed later. To accommodate for this change the skater s mass to.1 Kg without pausing the simulation. Q8: Wait until the skater comes to a complete stop. According to the graph, what is the relationship between the thermal energy and the total energy? (You can increase the coefficient of friction to slow down the skater more quickly.) Q9: In your own words describe how gravitational potential energy makes its way through energy conversions to thermal energy. Part 2 Push on the tool bar and recreate the half pipe for your skater as you did before in step 3 of part 1. Change the parameters to meet the needs of each of the following situations and observe how the skater reacts to in each environment. Then answer the questions and do the calculations asked. Situation 1: The skater is on Jupiter and has a mass of 1 Kg (ignore the fact that this is only about 22 pounds), he starts from 1 m above the ground and the ramp is frictionless. Situation 2: The skater is on the moon and has a mass of 9 Kg, he starts at 7 m above the ground and the ramp is frictionless. Situation 3: The skater is in space and has a mass of 6 Kg, he starts from 5 m above the ground and the ramp is frictionless. Q1: In which situation is the max velocity of the skater the fastest? (You may find it useful to open the applet in several windows to do a direct comparison.) Q2: Calculate the potential energy of all three skaters. Label your answers. Q3: At what height would the potential energy of the skater in situation 2 be equal to the energy of the skater in situation 1?

7 Q4: Calculate the potential and kinetic energy of the skaters in situations 1 and 2 at half of their respective initial heights. Label your answers. Q5: Calculate the velocity of the skaters in situations 1 and 2 at the lowest point of the ramp. Q6: Which skater is moving faster? Space Skater Part 3 1. Record skater s path: a. Using the flexible end points, create a very tall parabolic path for skater. Place him at the top of the hill on the left side. You can record skater s path using the record feature. Check it. b. Find the pause button and the live button. The live button will make skater begin skating. Click live to let him go on earth gravity and pause him when he maxes out on the other side. Repeat this pattern for moon and Jupiter gravity. Each dot represents an equal time interval. Draw what you see and compare the dot spacing for each gravity. c. What do you notice about the spacing pattern compared to gravity and what does it tall you about the maximum velocity for each gravity? d. Where is maximum velocity reached? Is it reached in the same spot for each gravity? e. Where does skater come to a stop before changing direction and heading back down? f. Ignoring atmosphere, temperature, etc., which gravity is most dangerous to skate on and why? g. Are the dots representative of skater s feet, or his center of mass?

8 2. Record acceleration due to gravity for the moon, earth and for Jupiter. Use the virtual tape measure and v = (2gh) to find out how fast skater is going at the bottom of the hill. What pattern do you notice for each gravity? Is it linear, proportional to square, square root, other? 3. Open the energy vs. time graph. Pause skater half way down, all the way and half way back up. Create and record thermal, KE and PE. What pattern do you notice? (Comment on conservation of energy, etc.) 4. Record energy vs. position for the entire run below: 5. What patterns do you notice from 4? Why? 6. Let the bar graph swing up and down and forth as skater moves up and down. Which items in the bar graph are opposites (one goes up while the other goes down? Are any of a similar pattern(goes up with other one goes up)?. 7. Mess around with gravity setting and the virtual tape measure. Find a gravity setting where spacing is twice that of earth and another where spacing is half that of earth. What gravities do you find? Can you offer any ideas for this result? 8. You are a space skateboard track designer. Create your own unique track for moon, earth and jupiterean skaters. How would they differ and why. Draw your design for a cool experience and explain how some designs are better than others and why yours takes advantage of the laws of physics to make the best skating experience possible for that planet!

9 Name Unit VII: Worksheet 3a For each situation shown below: 1. Show your choice of system in the energy flow diagram, unless it is specified for you. **Always include the earth in your system. 2. Decide if your system is frictionless or not, and state this. 3. Sketch an energy bar graph for the initial situation. 4. Then complete the analysis by showing energy transfers and the final energy bar graph. 1. Initial E k E g E e Energy Flow Diagram E k E g E e E int 2. Initial E k E g E e Energy Flow Diagram E k E g E e E int 3. y A car rolls to a stop while moving up a hill y = v > y > v = Initial E k E g E e Energy Flow Diagram E k E g E e E int

10 4. A person pushes a car, with the parking brake on, up a hill. y y = v = y > v = Initial E k E g E e Energy Flow Diagram E k E g E e E int 5. A load of bricks rests on a tightly coiled spring, then is launched into the air. y v > Initial E k E g E e Energy Flow Diagram E k E g E e E int y = v = Initial 6. A crate is propelled up a hill by a tightly coiled spring. y v > Initial E k E g E e Energy Flow Diagram E k E g E e E int y = v = Initial

11 ESPN Sports Figures: Tony Hawk in Perpetual Motion Video Guide 1. What is a perpetual motion machine? Can one really exist? 2. What is the equation for work? 3. How do you increase the gravitation potential energy of an object? 4. If an object is moving it is converting energy into energy. 5. What force makes the bowling ball, like all other objects, eventually slow down? 6. Where does the energy go? 7. Where is the average person s Center Of Mass? 8. What must a person do with their center of mass in order to speed up on a swing? 9. What does Tony Hawk do to keep from stopping in the half pipe?

12 1. What is the unit of work? 11. What law must Tony Hawk obey that proves the half-pipe is not a perpetual motion machine?

13 Name: No: Lab: Pop-Up Toy Phun! Purpose: Using the conservation of energy, calculate how fast a pop-up toy is moving just before it hits the table. List all steps in your procedure, show your data neatly in a table, and show a complete sample calculation on this lab sheet.

14 Physics and the 1 Acre Woods (Energy Transformations) Deep in the 1 Acre Woods, Tigger-- having rashly demonstrated that Tiggers love to climb up trees-- has found himself perched atop a tall hickory. Far below him (8. m to be exact), Christopher Robin, Rabbit, Kanga, and Roo are all holding the edges of a blanket and are trying to coax Tigger into dropping down since he refuses to climb. ("Tiggers don't climb down trees.") Tigger's mass is 35kg. Show ALL work and formulas in your NOTEBOOK! 1. What is Tigger's potential energy before he jumps? 2. What is Tigger's kinetic energy before he jumps? 3. What is Tigger's potential energy just before he reaches the blanket? 4. What is Tigger's kinetic energy just before he reaches the blanket? 5. How fast is Tigger moving just before he reaches the blanket? 6. What is Tigger's potential energy halfway down from the tree? 7. What is Tigger's kinetic energy halfway down from the tree? 8. What is Tigger's speed halfway down from the tree? Other Energy Questions: 9. A bird of mass 1.kg dives down to spear a fish out of an ornamental pond. If the bird is moving at 2.m/s when it is 1.m above the pond, how fast will it be moving when it reaches the water's surface? 1. A car is moving along a flat highway at 2.m/s when the brake line bursts. The driver, being a student of physics, drives the car up a nearby dirt hill. a) Neglecting the effects of friction, how high up the hill will the car go? b) Why should the driver still be concerned? 11. Why are perpetual motion machines impossible? 12. Two slides of equal height are side-by-side at a children's playground. Slide A has a 3 degree angle as measured from the horizontal. Slide B has a 6 degree angle. If child A slides down slide A and child B slides down slide B, which child will be moving the fastest at the bottom? 13. For the same slides, if friction is taken into account, how does your answer change?

15 Physics bowling ball on a ramp problems Names: Each Group turns this in. Write equations for PE and KE and what each variable stands for below: PE = KE = As a class: Assume you have an 8. kg bowling ball. The ball is released from a ramp down a 15 m long incline. The incline is sloped such that the elevation drops by 7 cm on the incline. Use conservation of energy to predict velocity at the bottom of the ramp. Draw a picture and as always, be sure to include proper units! With the others at your table: You have a 5 kg ball which you release down a ramp. The ramp elevation drops 5 cm. How fast should the ball be going at the bottom of the ramp?

16 Create a plan with your table mates on how you can do this outside the hall. Your object is to come up with a plan to get enough data to predict speed using conservation of energy and also come up with a way to measure Vf using Nifty Equations. Remember, Vf is twice the average speed. After you have time to create your plan, two representatives will have 5 minutes in the hall to do measurements and then you will get one chance to roll the ball down the incline. Write down your plan in steps below: Compare the Vf you measured to Vf predicted by conservation of energy. Use 4-steps. After you are done, you can work on homework while the other groups is taking their turn.

17 Unit 11 Physics Themed Vocabulary and Equations Rollercoaster Work/Energy Vocabulary: Joule Newton Kinetic energy Potential energy Gravitational potential energy Mechanical energy Elastic potential energy Chemical energy Nuclear energy Electrical energy Internal energy Deformation energy Sound energy Light energy Thermal energy Total energy Efficiency Friction Conservation of energy Frictionless Pendulum Perpetual motion machine Work Symbols: PE, KE, GPE, m, g, h, v Equations & constants: PE = mgh KE = ½mv 2 ME = KE + PE Weight = m * g g = 9.8 m/s 2 1 kg = 2.2 lbs 1 mile = 169 m 6 mph = 27 m/s Unit Objectives - Williams 1. I understand all the vocabulary & math of this unit and all demos, videos, equations, and class assignments; I remember objectives & vocabulary from previous units. 2. I understand what conservation energy means including common examples of real world exchanges of energy 3. I can to track the exchange energy for masses moving up and down hills while ME remains constant 4. Compute/graph energy totals & categories using GPE, KE, ME including using correct units and including how changes in mass, speed and height change the results 5. Compute weight/mass 6. Identify and understand other forms of energy in unambiguous situations 7. Follow energy flow in pendulums and rollercoasters including consequential changes in speed and position when heights are changed as well as novel situations; understand why first hill must be tallest 8. I can account for, but not directly calculate for friction/thermal energy including the unavoidable energy flow in that direction 9. I understand how to use each of the math equations, including what situations to use them, variable names, units and assumptions DuPage ROE Objectives 41. I can identify if masses have kinetic and/or potential energy at a given instant. 42. I can identify potential energy as a function of position. 43. I can identify kinetic energy as a function of velocity. 44. I can calculate gravitational potential energy and kinetic energy. 45. I can identify an isolated system and analyze it. 46. I can identify that energy is transferred between different forms. 47. I can solve problems using conservation of mechanical energy. 48. I can apply the mathematical definition of work as the product of Force and displacement. 49. I can identify situations of positive work, negative work, zero work. 41. I can identify work as a change in energy I can analyze the rate of energy change of a system in terms of power.

18 Rollercoaster Energy Calendar: (Williams) Bold and underlined means put in journal notes. 1 Mo:4/2/12 2C Tu:4/3/12 (11-1) Energy intro. Notes & sample problems (KE and PE) Concept development sheet (8-2) Conservation of energy video (p. 3, 4) (11-3) Go over different types of energy/conservation of energy A few energy practice problems together Skate park lab see conservation of energy in action, p. 5 8, possible computer lab quiz at end Conservation of energy examples (p. 9, 1) Tony Hawk video, p. 11, 12 (if time) (11-2) Notes: Reading packet 1, pages 1-4 Finish roller coaster energy problems started in class (11-4) Reading packet 1 problems: 3 12, (11-5) Reading packet 1 problems:: 23, 24, 26-28, (11-6) Reading packet 1 problems:: 29, 3, Finish p. 14 if not finished in class Extra practice problems if assigned in class 3H3 We:4/4/12 Ball O death? Mini lab: Pop up toy phun! p Additional energy practice, p. 14 (Tigger) Th:4/5/12 Begin HW 5 See if you remember NIFTY! Mo:4/9/12 Bowling ball challenge (p. 15, 16) QQT or clickers 6 Pairs review followed by pairs HW Quiz Tu:4/1/12 Start HW sheet if one is assigned in class Go over HW Quiz 7L We:4/11/12 Review day Study for test 8 Th:4/12/12 Energy & Coasters Test Possible sheet given in class