Physics Of Hovercrafts 2
Contents
1. then click on Animate So how do the two relate to one another Consider the hovercraft moving at a constant velocity across the gymnasium floor The craft person has a certain momentum p which equals the total mass multiplied by the velocity The more mass the greater momentum the lower the velocity the smaller the momentum Suppose the hovercraft were allowed to continue until it bumped into a wall and we could measure it with the force platform The momentum would be transferred into the wall then back to the hovercraft in the form of an mpulse which would likely result in the craft bouncing off the wall and going another direction This gets into a discussion of collisions which is another laboratory activity altogether For this exercise we will focus on the two parts and combine them later on This activity meets State of Texas TEKS requirements from 112 42 IPC c 4 A 112 47 Physics including items _ c 4 B C E and 5 B to D http www tea state tx us teks More details about these and other national science education teaching standards can be found at websites such as http www nsta org Equipment The equipment needed for this activity is as follows 1 PASCO Hovercraft with air supply 1 Meter stick Masking Tape Stopwatch 1 PASCO Xplorer GLX hand held data logger fully charged 1 PASCO Force Platform gt o o o Procedure In this experiment we will investigate forces momentum an2. student a chance to be the rider except that no markers will be needed in this case The pusher should hold the Force Platform perpendicular to the ground The rider should place the second Force Platform up against the pusher s The pusher should provide a force to the rider for about 1 second After moving across the floor for about 5 seconds stop the vehicle Answer the questions in the final section Questions Newton s First Law of Motion 1 Describe the motion both during and after the push Draw a force diagram for the rider both during and after the push Describe the position versus time and velocity versus time graphs you can print them out as well Based on the appearance of the velocity graph is the rider traveling at a constant velocity Describe the spacing between the marks on the floor and what is suggested about the motion of the Hovercraft Make a plot of the distance versus time based on stopwatch and mark data How does this compare with that of the Motion Sensor 5 Describe the causes of motion that you observed throughout the motion of the Hovercraft Questions Newton s Second Law of Motion 1 Describe the motion both during and after the pull Draw a force diagram for the rider both during and after the pull Describe the position versus time and velocity versus time graphs you can print the graphs as well Based on the appearance of the velocity graph is the rider trav
3. Hovercraft and rider a push but add some spin to the vehicle Try to get the vehicle to move as straight as possible so as to not collide with the walls Pick a point on the edge of the craft and time how long that point you can mark it with masking tape or something that stands out takes to make one rotation Also mark the location of the hovercraft at the start and end of the rotation If you were a fly on the ceiling watching what was going on below what would the shape of the path of the masking tape marker be the one rotating on the edge of the craft Draw it in the space below Measure the diameter of the hovercraft and calculate its circumference C aD Calculate the angular velocity with the formula d vt where d is the circumference C How does this value compare with the value of straight line velocity from point A to Point B
4. and forces There are many real world applications to the hovercraft as analogs of the laboratory model are used in daily life Some everyday examples include air cushioned vehicles or ACV s which travel atop a layer of compressed air and can travel over land or water These carry people vehicles or freight and can move at speeds up to 80 mph We will be investigating two seemingly unrelated topics in physics but we will ultimately tie them together This exercise is one of a series of related exercises involving the large PASCO hovercraft the original exercise which is a combination of these is on the Internet on the Project XLR8 Website The first part of the exercise is actually a primer to get the student used to the PASCO force platform The students will have the chance to see how jumps stomps steps and leaps show up on a graph that shows the force exerted versus time By measuring the peak of the graph the student will be able to directly see the force in Newtons exerted on the platform during the action Next we will use the hovercraft to see how straight line or translational motion compares to rotational or angular motion We will look at these individually then put them together to get a complicated motion called a cycloid To see a nice animation of a cycloid which shows a motion similar to what we will see with the Hovercraft only faster go to http www ies co jp math java calc cycloid cycloid html go to Applet 1
5. for the Hovercraft These can also be useful in exploring position velocity and acceleration Newton s First Law Several students will observe the motion one will be the catcher to stop the Hovercraft and another will be the marker to mark the motion of the craft with tape placed on the floor Set up the motion sensor connected to an Xplorer GLX so it will be able to measure the distance and velocity of the person on the hovercraft Press the Play button when you are ready to put the rider in motion Provide a brief push to the rider then start the stopwatch The marker will then mark the position of the hovercraft each second as well as at the start and end of a 5 second interval After the last mark is placed stop the Hovercraft Answer the questions in the final section Newton s Second Law Assign the same roles from Experiment 1 to different students and give another student a chance to be the rider Place the motion sensor behind the rider so as not to run over it when you pull the rider Press the Play button when you are ready to start Using a rope provide a constant force to the rider for about 3 seconds Have the marker mark the position of the Hovercraft each second After moving across the floor for 5 seconds stop the vehicle then stop the Motion Sensor Answer the questions in the final section Newton s Third Law Assign the same roles from Experiment 1 to different students and give another
6. own motion holding the motion sensor so that it points toward a wall which will serve as the object which will reflect the sound waves thus gauging your distance from the wall It may be helpful to have someone time you with a stopwatch calling out the time every five seconds e g 5 10 15 20 so that you can maintain your pace with the graph Compare your results with the actual plot below Visualizing Position Run 1 a E Q ro A 2 a O a a s E a S E E S E 17 19 21 23 25 27 29 Time sec Repeat the procedure now using Run 2 below Notice that this one is a bit more complicated and will necessitate quick moves on your part Visualizing Position Run 2 E Q c S g 2 Q LOCO P T T E T E T EN OE 15 17 19 21 23 25 27 29 Time sec Finally make similar graphs for each other to follow using pencil and ruler and graph paper Be challenging enough to make it interesting but be realistic as well the motion sensor has a range of 11 0 meters and people can run only so fast When you are finished with all this activity answer the following questions your teacher may have additional questions to go with these Results and Conclusions 1 Comme
7. standing in place on both feet then on one foot horizontal and vertical jumps pushups and anything else you can think of Make sure there are several seconds of time to give the display a chance to flat line so you can later tell one activity from another Once you have all the activities press the play button on the GLX once more to stop it and fill in the table on the following page Activity Measured value comments on the activity Activity is where you put the name of the activity and Measured value comments on the activity are where you put the times and comments For example you can put a value for the maximum force exerted by a single jump in place and add the height of the jump as measured by a group mate You can use the smart tool application on the graphical portion of the GLX to find the maximum force of a given action Having written each action down as it happens as well as including space between each action to enable a distinction to be made between each action it will be much easier to correctly identify each and correlate the correct value of force for each as measured by the GLX To think about How can you use some of the above activities to further your knowledge of energy momentum and impulse You can include the use of the entire profile of a given action not just the top of the peak Rotation versus translation motion Give the
8. travel over land or water These carry people vehicles or freight and can move at speeds up to 80 mph The large PASCO hovercraft provides an excellent opportunity to investigate Newton s three laws of motion experimentally The following exercise was adapted from the experiment and user s manual that came with the hovercraft We have reproduced it and changed it slightly for this exercise Some of the activity involves drawing vectors you should complete the Visualizing Vectors exercise before starting this one and the use of the force platform you should complete at least the first part of the Forces Motions and Hovercrafts exercise prior to starting this one This activity meets State of Texas TEKS requirements from 112 42 IPC c 4 A B 112 47 Physics including items c 4 C to E and 5 B to D http www tea state tx us teks More details about these and other national science education teaching standards can be found at websites such as http www nsta org Equipment The equipment needed for this activity is as follows 1 PASCO Hovercraft with air supply 1 Meter stick Masking Tape Stopwatch 2 PASCO Xplorer GLX hand held data loggers fully charged 2 Digital adaptors for the GLX 1 PASCO motion sensor 2 PASCO Force Platforms Procedure In this experiment we will investigate Newton s three laws of motion The activity is adapted from PASCO s Experiment and User Guide
9. Visualizing Vectors on the Force Table Royal High School Physics Fall 2007 Purpose and Introduction The following exercise adapted from one of the PVAMU Physics laboratory exercises is meant to serve as a primer for vectors from an experimental perspective Students may want to perform this experiment before performing any of the hovercraft experiments This activity meets State of Texas TEKS requirements from 112 42 IPC c 4 A B 112 47 Physics including items c 4 C to E and 5 B to D http www tea state tx us teks More details about these and other national science education teaching standards can be found at websites such as http www nsta org A vector is a mathematical object used to represent quantities which have two or more independent dimensions such as magnitude and direction We are going to visualize vectors using two methods experimental and graphical The purpose of this exercise is to familiarize the student with how vectors work and how they add together To investigate the nature of vector addition experimentally we will use a force table to add two vectors by measuring the net effect of the forces when the system is at equilibrium Experimental steps Procedure 1 Case 1 Put 150 grams on A and B two vectors and position them at 45 and 135 degrees Add masses to the negative of the resultant R the vector that results when you add the first two together and vary the angle of t
10. d motion and how these tie together In the first part we get acquainted with the force platform and find out how simple actions such as footsteps and jumps appear on a force versus time plot We will look at these plots a bit more closely to see which ones are more pronounced Students are encouraged to try a variety of steps jumps and exercises including push ups standing on one foot versus two etc and see how these register on the time versus force plot We will then look more closely at the physics behind these actions Second we will investigate motion both the linear also called translational and the circular angular forms We will learn how they work together to produce a more complicated motion as seen from a stationary reference point The Forces of Steps Jumps and Leaps We will look at the force platform by itself first this will be used again in a separate exercise Connect the platform to the Xplorer GLX and make sure it is displaying the graph of force versus time Once everything is set up properly hit play on the GLX and make sure a graph is plotting Do a series of activities one at a time in a well defined sequence so you can pick out one from another It would be a good idea for a group mate to write down the nature of each activity that affects the force platform to enable better correlation of activity to parts of the plot The activity will include a footstep while walking a footstep while running
11. eling at a constant velocity Describe the motion of the hovercraft based on the spacing between the marks on the floor Make a plot of the distance versus time based on stopwatch and mark data How does this compare with that of the Motion Sensor Describe the causes of motion that you observed throughout the motion of the Hovercraft Questions Newton s Third Law of Motion 1 Describe the motion both during and after the push 2 Make a graph from the Force Platform data showing both the pusher s force and the rider s force 3 Draw force diagrams for both the pusher and rider during the push 4 Formulate a general rule about the size and direction of forces between two objects For Further Thought You probably have done one or more activities in addition to this one which were meant to illustrate one or more of Newton s laws of motion How are the activities similar What is different about them Specifically describe the common features of all the activities meant to show Newton s Laws of motion Forces Motions and Hovercrafts Royal High School Physics Fall 2007 Purpose The purpose of this activity is to investigate several interrelated physics concepts using a PASCO force platform and a PASCO hovercraft Introduction to the Activity The hovercraft provides many fun opportunities to do demonstrations and experiments involving brave student volunteers studying the concepts of momentum collisions velocity vectors
12. ger Meter stick PASCO motion sensor Several sheets of graph paper Stopwatch or timer o o Procedure The Motion Sensor works by putting out pulses of sound and converting the travel times to distance It works with the knowledge of the speed of sound in air 331 4 m sec and the fact that the round trip travel time multiplied by this speed value divided by two gives the distance to an object The object reflects the sound pulses back to the Motion Sensor which makes it possible to calculate the distance to the object The device makes 10 measurements per second and usually plots these values on a distance versus time graph The software that works with the motion sensor can also calculate velocity by taking the differences between each consecutive reading of position and converting that to a velocity value It can also display acceleration by taking the differences between consecutive velocity values You will be studying the relationship between position velocity and acceleration in class but we will start with position in this exercise It may be helpful to play around with the motion sensor for a few minutes before starting this exercise That way you can get a feel for how it works and how changing your position changes the appearance of the graph of distance versus time as it is being plotted Also study the graphs which both span 30 seconds and plan how to move in order to match these graphs Match graph 1 with your
13. he resultant until the circle is balanced in the middle of the force table Don t forget to include the mass of the weight hanger 50g When this occurs a state of equilibrium exists and the sum of the vectors should be zero Add these same two vectors graphically scale their lengths so that 150g 1 5cm on the graph use a separate sheet of graph paper for this measure the angle and length of the resultant and compare that to the force table resultant 2 Calculate the force on each vector in SI units for Case 1 You will need to convert measured values in grams to kg and then remember that A is a force vector and so must be in Newtons A mg Values should be stated using 3 significant figures D the same for B and R and write your results in the space below 3 Draw a picture of the force table top with all vectors used in part 1 labeled correctly 4 Work the following cases following the bulleted list of exercises for Case 1 Be sure to convert all masses to Newtons as described in 2 for the final answers Case 2 A 100 grams at 45 degrees B 100 grams at 110 degrees A N B N R N at degrees Case 3 A 150 grams at 15 degrees B 200 grams at 60 degrees A N B N R N at degrees Case 4 A 50 grams at 0 degrees B 150 grams at 90 degrees A N B N R N at degrees Case 5 A 50 grams at 0 degrees B 150 grams at 75 degrees C 100 grams at 90 degrees A N B N C N R N at degrees Visual
14. izing Motion with PASCO s Motion Sensor Royal High School Physics Fall 2007 Purpose The purpose of this activity is to visualize motion with the PASCO motion sensor and to use the sensor to match graphs of position versus time using the student as the object in motion An important skill to have is to be able to look at a graph and to tell what it is communicating An excellent way to get practice with this is to make your own graphs Graphs are an excellent way to tell a lot of information without using a lot of words We will look at some graphs of position versus time If the position stays the same we see a horizontal line on the graph If the position changes the line is tilted or curved depending on how it changes over time The change in position over time is referred to as velocity or motion We will ultimately investigate position velocity and acceleration and see how they are related to each other However we will stick to position for this exercise This activity meets State of Texas TEKS requirements from 112 42 IPC c 4 A C 112 47 Physics including items c 4 A C and E http www tea state tx us teks More details about these and other national science education teaching standards can be found at websites such as http www nsta org Equipment The following will be needed to perform the experiment successfully PASCO X plorer GLX handheld data logger Digital adaptor for the datalog
15. nt on how difficult or easy it was to match the graphs that were provided with this exercise and also by your classmates 2 What was happening when the line was horizontal Why 3 What was happening when the line was tilted and how does the steepness of the tilt relate to what happened 4 How do these graphs show the relationship between position and velocity 5 Is the Motion Sensor accurate Place the sensor preferably mounted on a support rod stand for steadiness exactly 2 0 meters from the wall and activate Set the readout to Digits mode and take a few random numbers from the readings up to 5 numbers and take the average of these Does the average equal 2 0 If not why not How far off was the Motion Sensor if it read an incorrect distance Hovercrafts and Newton s 3 Laws of Motion Royal High School Physics Fall 2007 Purpose The purpose of this activity is to investigate Newton s 3 Laws of Motion using a PASCO force platform motion sensor and hovercraft Introduction to the Activity The hovercraft provides many fun opportunities to do demonstrations and experiments involving brave student volunteers studying the concepts of momentum collisions velocity vectors and forces There are many real world applications to the hovercraft as analogs of the laboratory model are used in daily life Some everyday examples include air cushioned vehicles or ACV s which travel atop a layer of compressed air and can
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