Youngstown City Schools
SCIENCE: PHYSICS
UNIT #2: INTRODUCTION TO MOTION- - (6 Weeks) 2013-2014
SYNOPSIS: This unit focuses on the concepts and relationships of displacement, time, speed, and velocity. Students explore freely falling bodies as examples of motion with constant acceleration. They collect and use data to construct and interpret graphs. Students demonstrate their knowledge of physics and engineering concepts by designing and building their own working small scale roller coaster that contains vertical and horizontal loops, bunny hills, and jumps.ENABLERS: acceleration, average acceleration, average velocity, constant acceleration, displacement, free fall, free-fall acceleration, velocity, and force
STANDARDS
IV. MOTION
A. Use and apply the laws of motion to analyze, describe and predict the effects of forces on the motions of objects mathematically.
B. Analyze velocity as a rate of change of position with regards to average velocity and instantaneous velocity.
C. Compare and contrast speed, velocity, distance and displacement as scalar and vector quantities.
D. Analyze acceleration as rate of change in velocity.
E. Use graphical and mathematical tools to design and conduct investigations of linear motion and the relationships among position, average velocity, instantaneous velocity, acceleration and time.
F. Graph and interpret graphs on position vs. time, velocity vs. time, and acceleration vs. time.
G. Instantaneous velocity for an acceleration object can be determined by calculating the slope of the tangent line for some specific instant on a position vs. time graph.
H. Introduction of complex graphs that have both positive and negative displacement values and involve motion that occurs in stages. Symbols representing acceleration are added to motion diagrams.
I. The determination of uniform acceleration including free fall (initial velocity, final velocity, time, displacement, acceleration, average velocity).
J. Interpreting graphs for average velocity, instantaneous velocity, acceleration, displacement, and change in velocity.
LITERACY STANDARDS
RST.4 Determine the meaning of symbols, key terms, and other domain-specific words and phrases as they are used in a specific scientific or technical context relevant to grades 11–12 texts and topics.
WHST.6 Use technology, including the Internet, to produce, publish, and update individual or shared writing products in response to ongoing feedback, including new arguments or information.
WHST.7 Conduct short as well as more sustained research projects to answer a question (including a self-generated question) or solve a problem; narrow or broaden the inquiry when appropriate, synthesize multiple sources on the subject, demonstrating understanding of the subject under investigation.
WHST.9 Draw evidence from information texts to support analysis, reflection, and research.
MOTIVATION / TEACHER NOTES /1. A demonstration on displacement (Holt Physics TE page 42, demonstration 1).
2. A demonstration on acceleration (Holt Physics TE page 48, demonstration 2).
3. Distance learning activity on the physics of roller coasters
4. Students set both personal and academic goals for this Unit.
5. Preview the authentic assessment
TEACHING-LEARNING / TEACHER NOTES /
1. Students (a) calculate their reaction time in catching a meter stick that is falling; (b) analyze and graphically show the results of the activity; (c) make hypotheses about reaction time (e.g., left handed people have faster reactions than right handed people, etc.). Students design, and carry out their experiments, gather and present data graphically, and explain clearly and concisely the results of their experiment to the class. If their conclusions are different than their hypotheses, they revise their experiment to gather new data. (WHST.7) (IVB,IVI)
2. Teacher explains the relationships between displacement, time, speed, and velocity. Students complete practice problems on these concepts. Students break into small groups and analyze each other’s practice problems for accuracy, technique, correct formula use, and thought processes. Teacher leads discussion on correctness of the calculations. Use remediation as necessary. (IVC,IVF) (RST.4)
3. Teacher demonstrates the difference between accelerated and non-accelerated motion by walking around the room. Ask students to identify when the motion is accelerated and when it is uniform. Students take notes and generate questions for discussion. (IVD)
4. Students read and discuss information on the design of roller coasters to broaden their knowledge base on roller coaster forces by exploring the information on the following websites: http://library.thinkquest.org/C005075F/English_Version/Designing%20the%20Roller%20Coaster.htm)
http://www.math.wpi.edu/Course_Materials/Calc_Projects/node6.html
http://www.math.wpi.edu/Course_Materials/Calc_Projects/node6.html
(WHST.7) (IVA, B, C)
5. Students demonstrate how to design and build a roller coaster to determine, speed and velocity of a marble. They graph their results for different points on the coaster. (e.g., top of first hill, bottom of first hill, etc.) (IVC, F, G, H, I) (WHST.6, WHST.7)
6. Teacher demonstrates the relationship between the direction and the magnitude of a force (Holt Physics TE page 126, demonstration 2). (IVA, IVB) (RST.4) Students solve practice problems. Follow with a class discussion focusing on key terms, as they are used in this context.
7. Students calculate and graph the acceleration of a vehicle down slopes of different heights and lengths. Teacher leads a discussion of the class results. (IVE, IVF) WHST.7)
8. Teacher explains uniform acceleration and how to calculate the initial velocity, final velocity, average velocity, and acceleration. Students practice problems and then use this information to determine and graph the velocity of an egg in the egg drop experiment (IVG,IVH, IVI, IVJ) (WHST.7, WHST.9)
9. Students use egg drop data to calculate acceleration and final velocity of the egg apparatus. (attached page 4-5) Class discussion follows.
10. Students complete lab “Mousetrap Racers” attached on pages 6-9
TRADITIONAL ASSESSMENT / TEACHER NOTES
1. Unit Test: Multiple Choice and 2/4 point response questions
TEACHER CLASSROOM ASSESSMENT / TEACHER NOTES
1. Lab reports or practical reports using rubrics for quality points
2. Assignments and in class work
AUTHENTIC ASSESSMENT / TEACHER NOTES /
1. The students demonstrate their knowledge of physics and engineering concepts by designing and building their own working small scale roller coaster, with teacher supplied materials that contain vertical and horizontal loops, bunny hills, and jumps.
2. Students evaluate their goals for the Unit.
3. Students demonstrate their knowledge of physics and engineering concepts by designing a roller coaster on an IPAD or computer simulator to test for speed, velocity, and g-forces.
Name ______
Parachute Egg Drop
Objectives: Students will drop parachuted eggs to demonstrate the concepts of gravity, air resistance, and terminal speed. Students will construct distance and velocity graphs to interpret the acceleration of an object.
Pre-Lab Theory
Gravity is the force of attraction that causes objects to fall toward the center of the earth. Air resistance, or air friction, can slow down the acceleration of a falling object.
The area “fronting the wind” affects the amount of air resistance a falling object encounters. Terminal speed is the speed at which the downward pull of gravity is balanced by the equal and upward opposing force of air resistance for a falling object.
Materials
· Lightweight plastic kitchen garbage-can liners; Scissors; Ruler; 20-inch lengths of light string; 3 plastic sandwich bags; 3 raw eggs
Procedures
1. From a lightweight plastic kitchen garbage-can liner, cut out three squares. Make one square 10” x 10”, a second square 20” x 20”, and a third square 30” x 30”.
2. Make a parachute out of each square by tying a piece of string to each corner of the square, then attaching the other ends of the strings to a plastic sandwich bag.
3. Place a raw egg in each of the sandwich bags.
4. Predict which egg has the best chance of surviving a drop from about ten feet from the floor. Explain the reasoning behind their predictions.
5. Drop each unfurled egg parachute from a height of ten feet, and then determine whether or not your predictions were confirmed.
Discussion Questions
1. Describe the changing forces that acted on the parachutes as they fell and the resulting changes in the parachutes’ motion. How did the falls of the larger parachutes differ from the falls of the smaller ones?
2. Construct a distance vs. time graph for the following data: (D1 = 0 m, T1 = 0 sec), (D2 = 7 m, T2 = 3 sec), (D3 = 14 m, T3 = 6 sec), (D4 = 21 m, T4 = 9 sec), and (D5 = 28 m, T5 = 12 sec). Discuss how you would use this graph to determine the speed of the object being represented. Is the object moving with constant speed or constant acceleration? Explain how you arrived at your conclusion.
From the graph constructed in question 1, calculate the object’s speed at three-second intervals, and then use this new information to construct a velocity vs. time graph for the object.
Parachute Egg Drop
Distance / Time / Velocity / Acceleration10” x 10”
20” x 20”
30” x 30”
10” x 10”
20” x 20”
30” x 30”
10” x 10”
20” x 20”
30” x 30”
Physics Mousetrap Racers
Situation: Your mission is to design and construct a car powered by a standard-size mousetrap. Most people choose four-wheeled cars, but three-wheeled cars also exist. Some ways to increase your distance are replacing the string that pulls the axle with a rubber band. Larger wheels will increase the distance obtained using the same amount of energy. Using more string than what is needed will cause the string to rewind around the axle after the string runs out.
Problem: The objective is to design the lightest possible device that can travel at least 50 feet.
Pre-Lab Theory: A mousetrap is powered by a helical torsion spring. Torsion springs obey an angular form of Hooke's law: where is the torque exerted by the spring in Newton-meters, and is the angle of twist from its equilibrium position in radians. is a constant with units of Newton-meters / radian, variously called the spring's torsion coefficient, torsion elastic modulus, or just spring constant, equal to the torque required to twist the spring through an angle of 1 radian. It is analogous to the spring constant of a linear spring. The energy U, in joules, stored in a torsion spring is: When a mousetrap is assembled, the spring is initially twisted beyond its equilibrium position so that it applies significant torque to the bar when the trap is closed.
The mousetrap bar travels through an arc of approximately 180 degrees. This motion must be used to turn the car's axle or wheels. The most common solution is to attach a string to the bar and wrap it around an axle. As the bar is released, it pulls on the string, causing the axle (and wheels) to turn. Tying the string directly to the mousetraps bar, however, will not make good use of the energy stored in the spring. The distance between the opened and closed positions of the bar of a mousetrap is typically 10cm, so this is how much string would be pulled. Wrapped around even a small diameter axle, this amount of string will not create enough revolutions to move the car as far as it might go. To get around this problem, most mousetrap cars add a lever to the bar so that the lever will pull a much greater length of string and cause the axle to turn many more revolutions.
Another reason to add a lever to the mousetrap bar is to reduce the amount of torque applied to the wheels. If too much torque is applied to the wheels, the force between the wheels and the ground will exceed the maximum frictional force due to the coefficient of friction between the wheel and ground surfaces. When this happens, the wheels slip and energy stored in the spring is wasted. Using a long lever on the mousetrap bar reduces the tension in the string due to the spring's torque, and thus reduces the torque applied to the car's wheels. In addition to reducing the torque applied to the wheels, the coefficient of friction may be improved by using higher friction materials, such as rubber, on the wheels.
Design Constraints
· The Mousetrap car must be initially powered by the Mousetrap mechanism.
· The initial energy may be transferred to another device ONLY if that device does not produce energy by itself.
· NO other energy source may be added (e.g. CO2 cartridge, battery, etc.)
· The mousetrap must be permanently mounted to the chassis.
· All Mousetrap Cars must be made by students. No pre-constructed materials allowed.
Suggested Materials:
Mousetrap (provided), pens, eye hooks, CDs, vinyl record albums, string, clay or axle clogs (wheel kit), wheel axles, scraps of wood, glue, empty thread spools or other large circular item, balsa wood, metal rods, washers
Competition
1. Each car will use ONLY one standard size mousetrap.
2. The distance that a car travels will be measured to the point where the car leaves the designated track area from the starting line to the wheel closest to the starting line.
3. Each Mousetrap Car will be allowed 2 trials. The BEST will be recorded in a single run.
4. Each car must be ready for competition when called.
5. If you are not ready/prepared to race, you will forfeit your turn.
6. Two forfeits equal a disqualification.
7. Each car will be assigned a random number and there will be two rounds of trials.
Awards
Most Creative (most unique design): First, second, and third place.
Mechanical Design: First, second, and third place.
Distance Traveled Up Farthest: First, second, and third place.
7/082013 YCS Science: PHYSICS - Unit 2 - - INTRODUCTION TO MOTION 2013-2014 1