Introductory Energy & Motion Lab P4-1350

Transcription

1 Introductory Energy & Motion Lab P BACKGROUND: Students love to get to work fast, rather than spending lab time setting up and this complete motion lab lets them quickly get to the task of collecting and analyzing data! The ramp for the Energy and Motion Lab adjust to 10, 20, and 30-degree angles, so students can use the same equipment to explore velocity, acceleration, gravity, kinetic energy, friction, and more! This teacher-developed guide includes a comprehensive acceleration and mechanical energy labs that lets students inquire into the changes in a car s speed and energy as it accelerates down the ramp. In the first lab they ll take careful measurements, calculate averages, and see that the car s acceleration is a constant value. Demonstrate that the car s acceleration changes when the ramp angle is changed. In the second lab, the students will look at the changes in potential and kinetic energy and discover conservation of energy. BEESPI V: This lab incorporates our new BeeSpi V Advanced Self-Contained Photogate. Use the BeeSpi V to measure free fall speeds, cars and projectile velocities. Two parallel photogates detect, measure, and display speeds of any objects that pass through, from zero to km/h. Since it uses dual photogates, speed can be found with the object s front edge! No length measurement is needed. Try positioning BeeSpi sensors at different points on the inclined track, and calculate energy transformation from potential to kinetic. Objects larger than the 40mm x 30mm gap can be measured by attaching a flag to them. KIT CONTENTS: Adjustable Ramp 6ft Track Friction Motor Car BeeSpi V Photogate Timer BeeSpi Adapter Mounting Bracket This Teachers Guide *Included BeeSpi Mounting Brackets are required to properly place the Photogate so that the track can pass through it.* 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 1 of 13

2 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: TEACHER S NOTES: PURPOSE: For a car rolling down an incline, investigate the relationships between distance, time, velocity, acceleration and angle of incline. STUDENT BENCHMARKS: 1. Qualitatively describe and compare motion in two dimensions. Key concepts: Two-dimensional motion up, down, curved path. Speed, direction, change in speed, change in direction. Real-world contexts: Objects in motion, such as thrown balls, roller coasters, cars on hills, airplanes. 2. Relate motion of objects to unbalanced forces in two dimensions. Key concepts: Changes in motion and common forces speeding up, slowing down, turning, push, pull, friction, gravity, magnets. Constant motion and balanced forces. Additional forces attraction, repulsion, action/reaction pair (interaction force), buoyant force. Size of change is related to strength of unbalanced force and mass of object. Real-world contexts: Changing the direction changing the direction of a billiard ball, bus turning a corner; changing the speed car speeding up, a rolling ball slowing down, magnets changing the motion of objects, walking, swimming, jumping, rocket motion, objects resting on a table, tug-of-war. ADDITIONAL REQUIRED EQUIPMENT: Wooden Block Tape Meter stick Calculator TIME REQUIRED: 2-3 class periods or more. Successive classes can use intervals marked by the first class of the day. Just make sure to use the same car and ramp each time. If time is short, let students skip the 20 o ramp angle ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 2 of 13

3 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: BACKGROUND: Measurement of the motion of a freely falling object is difficult because the speed constantly increase. In fact, it increases by about 10 meters per second every second. The distance that the object falls each second becomes very larger, very quickly. Studying acceleration can be made simpler if this motion is slowed down by the use of an inclined plane (ramp), which makes the change in velocity easier to see because the change happens more slowly. The less steep the incline, the smaller the acceleration. This experiment will require you to make many timing measurements using the BeeSpi Photogate. This will allow your students to collect accurate data using new technology and minimize errors due to reaction time. The BeeSpi Photogate is actually two photogates in one. Have your students look closely at the inside of the BeeSpi. They will see two pairs of electronic light sensors. When the car passes through one, and then the other sensor, the BeeSpi measures the time elapsed between the two gates. The speed displayed is the distance between the gates divided by the measured time. PRE-LAB ACTIVITY: This pre-lab activity will demonstrate the importance of this type of measurement. Ask students to mark a known distance using start and finish lines on the flat section (Beyond where the track is inclined due to the ramp.) of track. Roll the car down the ramp, and use stopwatches to time the car s trip through the marked area. Calculate the average speed. Repeat the experiment several times, launching the car from the same spot each time. The results will probably vary a lot, due to human reaction time in using the stopwatch. Now, set up the BeeSpi Photogate on the level part of the ramp at the finish line you previously marked. Repeat the speed trial several times again, and note that the BeeSpi gives much more consistent results. LAB: FINDING ACCELERATION DOWN THE RAMP PROCEDURE: 1. Set up ramp with the 10 angle wedge. 2. Place the BeeSpi Photogate at the bottom of the straight portion of the ramp (just before the ramp begins to curve) ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 3 of 13

4 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: 3. Measure the distance d from the front of the car when it is at the top of the ramp to the middle of the BeeSpi Photogate when it is at the bottom of the ramp. 4. Press and hold the button on the BeeSpi Photogate for about 2 seconds, and release. You should see m/s flashing. If not, repeat until you do. The BeeSpi is now ready to record the velocity of the car. (Note: You will need to push the button after every measurement so that the m/s is flashing to record the new velocity). Release the car at the top of the ramp. Record the velocity (from the BeeSpi) in your Data Table. 5. Repeat the measurement for this same stop point four more times, resetting the BeeSpi and stopwatch each time. Record each velocity (from the BeeSpi) and the average of the five trials in your Data Table under the 10 o section. 6. Set the ramp at 20 o. Repeat steps 3-5, recording all measurements in your Data Table under the 20 o section. 7. Set the ramp at 30 o. Repeat steps 3-5, recording all measurements in your Data Table under the 30 o section. 8. For each angle we know three values of the cars motion down the ramp. First the starting speed of the car is zero at the top of the ramp V i. Second, we know the distance d it traveled from the top to the bottom of the ramp where speed was measured with the BeeSpi Photogate. Third we know the final speed at the bottom V f. The common way to calculate acceleration is to divide the change in velocity of the car by the time to speed up. However, in this experiment the time from the start to the bottom of the ramp is unknown and difficult to measure. Therefore, we will choose an alternate formula that uses the measured distance down the ramp to calculate the average acceleration. Using the formula below for which the starting speed is zero, we can calculate the average acceleration of the car on the ramp for each ramp angle. 2 V f Acceleration = 2d 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 4 of 13

5 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: 10 o Distance d (m) V o (m/s) V f (m/s) Acceleration (m/s 2 ) Trial #1 Trial #2 Trial #3 Trial #4 9. Complete the Data Table by finding the Acceleration for each ramp angle. Data Table 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 5 of 13

6 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: Trial #5 20 o Distance d (m) V o (m/s) V f (m/s) Acceleration (m/s 2 ) Trial #1 Trial #2 Trial #3 Trial #4 Trial #5 30 o Distance d (m) V o (m/s) V f (m/s) Acceleration (m/s 2 ) Trial #1 Trial #2 Trial #3 Trial #4 Trial #5 COMPLETE THE FOLLOWING ITEMS ON A SEPARATE SHEET Questions: 1. What is Acceleration? 2. Does the car accelerate down the ramp? Explain. How do you know? 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 6 of 13

7 LAB #1: INTRODUCTORY VELOCITY AND ACCELERATION Name: 3. What happens to the acceleration as the angle of the ramp is increased? Share specific data to support this. 4. In general, as the distance the car travels down the ramp increase, what happens to its velocity? Share specific data to support this. 5. In general, as the distance the car travels down the ramp increase, what happens to its acceleration? Share specific data to support this. 6. What would be the steepest angle the ramp could be set at? Predict the car s acceleration at this angle. Extension: As you should have predicted, the acceleration down the ramp increased as the angle of the ramp increased. A prediction of the free fall acceleration due to gravity g can be found by dividing the value of acceleration a at any ramp angle by the sine function of the ramp angle. g = a/ sin θ 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 7 of 13

8 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: TEACHER S NOTES: PURPOSE: For a car rolling down an incline, investigate conservation of energy through the transformation of potential energy to kinetic energy. When friction is negligible the decrease in gravitational potential energy will equal the increase in kinetic energy and allow the student to predict the speed or kinetic energy at a given height. Sample STUDENT BENCHMARKS: 6th Grade-Level Content Expectations (Michigan Dec 2007) Qualitatively describe and compare motion in two dimensions. ADDITIONAL REQUIRED EQUIPMENT: Wooden Block Tape Meter stick Calculator TIME REQUIRED: 1-2 class periods. Successive classes can use intervals marked by the first class of the day. Just make sure to use the same car and track each day ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 8 of 13

9 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: BACKGROUND: Measurement of the motion of a freely falling object is difficult because the speed constantly increase. In fact, it increases by about 10 meters per second every second. The distance that the object falls each second becomes very larger, very quickly. Studying acceleration can be made simpler if this motion is slowed down by the use of an inclined plane (ramp), which makes the change in velocity easier to see because the change happens more slowly. The less steep the incline, the smaller the acceleration. This experiment will require you to make many timing measurements using the BeeSpi Photogate. This will allow your students to collect accurate data using new technology and minimize errors due to reaction time. The BeeSpi Photogate is actually two photogates in one. Have your students look closely at the inside of the BeeSpi. They will see two pairs of electronic light sensors. When the car passes through one, and then the other sensor, the BeeSpi measures the time elapsed between the two gates. The speed displayed is the distance between the gates divided by the measured time. Students will measure the car s speed at five different spots on the ramp, and calculate the kinetic and potential energy at each point. They will analyze the data and determine that most of the potential energy is converted to kinetic energy, but some is lost to other forms. This will be especially evident in the flat part of the track at the end. PRE-LAB ACTIVITY: Although the frictional force on the ramp is low, it will affect you predictions. We can measure this affect by finding the speeds of the car as it travels along the bottom flat portion of the ramp. Set the ramp up using the 20 angle wedge. Use two BeeSpi Photogates, one at the beginning of flat portions of ramp at the bottom and the second near the end. Start the car at the top of the ramp and allow it to travel down the ramp while passing through the two photogates. Knowing the two speeds and the mass of the car, calculate the car s change in kinetic energy. Dividing this change in energy by the distance between the photo gates will give an approximate value for the force of friction on the car. LAB: CONSERVATION OF MECHANICAL ENERGY In this lab Mechanical Energy refers to the sum of the car s gravitational potential energy and its kinetic energy. When friction is negligible the sum of these values should remain constant or be conserved ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 9 of 13

10 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: PROCEDURE: 1. Set up ramp with the 20 angle wedge. 2. Place the car at the very top of the ramp and mark the position of front of the car with mark on the side of the ramp using a washable marker. This is point 1 on the data table. 3. With a meter stick held vertical next to the mark, measure the height of the track at this top position. (Remember to subtract for the thickness of the track.) 4. Move down the track a vertical distance of 5.0 cm and mark this as point 2 on the side of the track. 5. Repeat this process down the track 5.0 cm each time until you have 5 position points. This should be just above the point on the track where it is no longer elevated. 6. The last point to mark (point 6) is a place on the track where it flattens out on the level surface. This has a height of 0.0 cm or 0.0 meters. Change all the above heights to meters and record these heights (in meters) in the Data Table Under the correct position points. 7. Measure the mass of the car. Record (in kg) in the Data Table. 8. At point 1 at the top of the ramp where the car will be released, the speed of the car will be zero and therefore the Kinetic Energy will be zero. Place the BeeSpi Photogate at point 2 below the top so that it is centered on the mark you made earlier. 9. Press and hold the button on the BeeSpi Photogate for about 2 seconds, and release. You should see m/s flashing. If not, repeat until you do. The BeeSpi is now ready to record the velocity of the car. (Note: You will need to push the button after every measurement so that the m/s is flashing to record the new velocity. Release the car at the top of the ramp. Record the velocity (from the BeeSpi) in your Data Table ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 10 of 13

11 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: 10. Repeat the measurement for this point four more times, resetting the BeeSpi each time. Record the speed for each of the five trials and the average on the Data Table. 11. Repeat steps 9 & 10 with the BeeSpi at each of the three lower points. Be sure to throw out and redo any measurements where the car hits the timer or the tack. 12. Complete the Calculated Data Table by finding the Potential Energy, Kinetic Energy, and Kinetic + Potential Energy for each point. 13. The addition of the Kinetic Energy and the Potential Energy is known as the Mechanical Energy. Find the average of Mechanical Energy for all five points. potential energy = mass height 9.8 m s! Hint: kinetic energy =! mass (velocity)!! COMPLETE THE FOLLOWING ITEMS ON A SEPARATE SHEET Conclusion: Write 5-6 sentences about what you have seen and learned about energy today in lab. Be sure to include something about how energy transforms from potential to kinetic, and what happens to the total energy of the car ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 11 of 13

12 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: Data Table Car mass = kg Point 1 Height (m) = Velocity (m/s) Point 2 Height (m) = Velocity (m/s) Point 3 Height (m) = Velocity (m/s) Point 4 Height (m) = Velocity (m/s) Point 5 Height (m) = Velocity (m/s) Point 6 Height (m) = Velocity (m/s) Calculated Data Table 2014 ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 12 of 13

13 LAB #2: INTRODUCTORY ENERGY TRANSFORMATION Name: Energy Transformation Calculations Point 1 Point 2 Point 3 Point 4 Point 5 Potential Energy (J) Potential Energy (J) Potential Energy (J) Potential Energy (J) Potential Energy (J) Kinetic Energy (J) Kinetic Energy (J) Kinetic Energy (J) Kinetic Energy (J) Kinetic Energy (J) PE + KE (J) PE + KE (J) PE + KE (J) PE + KE (J) PE + KE (J) Questions: 1. To increase the Potential Energy of the car, you would increase the of the car. 2. To increase the Kinetic Energy of the car, you would increase the of the car. 3. What happens to each type of energy as the car progresses down the ramp? 4. What happens to the total energy (potential + kinetic) as the car progresses down the ramp? Share specific data to support your answer. 5. Is Mechanical energy conserved in this situation? Explain. 6. Calculate the potential energy of the car when it is 16 cm (0.16 m) above the bottom of the track. Next using the Mechanical Energy from the five points, predict what the car s Kinetic energy would be at this point. 7. Release the car from the top of the ramp and use the BeeSpi Photogate to measure the speed at this point. Calculate its Kinetic Energy here and compare it to value obtained in question 6. Why should they be nearly the same. Extension: Using a spreadsheet, plot your data with kinetic energy (vertical axis) vs. potential energy (horizontal axis) ARBOR SCIENTIFIC ALL RIGHTS RESERVED Page 13 of 13