Experiment 1: Balancing Centripetal ForceIn this experiment, you will investigate how the magnitude of radius affects the time period of an object with circular motion. Materials1 Aluminum Tube1 m. Fishing Line(5) Metal WashersPermanent MarkerScissorsStopwatchTape MeasureProcedure1. Measure out and cut one meter of fishing line. 2. Tie a single metal washer around one end, and string the other end through the tube.Tie four washers at the other end in a group (Figure 6). 3. Measure 0.25 m from the single washer and use a permanent mark to mark this pointon the line. 4. Hold the tube vertically at arm's length to your side so that the washer near the mark is hanging from the top. 5. Hold a stopwatch in your other hand or get a willing participant to help you make time measurements. 6. Begin swinging the tube so that the top washer rotates in a circle. Increasing the speed of rotation (careful, not too fast!) should change the radius rotation. 7. Vary your speed until the mark you made on the line is at the top of the tube, making the radius of rotation 0.25 m. 8. At this speed, time how long it takes to make 15 revolutions. Record your values in the Table 1. 9. Make a new mark at 0.40 m and repeat Steps 3 - 8. Record your measurements Table 1. 10. Make a third mark at 0.15 m and repeat Steps 3 - 8 again. Record your measurements Table 1. Table 1: Rotational DataRadius Time per 15 Period (s) Expected Percent© 2014 eScience Labs, LLC.All Rights Reserved(m)revolutions(s)Value Error (%)0.25 7.78 .52 .502 3.18% 0.40 9.24 .62 .634 2.83%0.15 5.37 .36 .388 7.73%Post-Lab Questions1. Compare your measured data to your predicted values with a percent error calculation. Explain any differences with an error analysis.Possible reasons for error:- Experimental setup error- Personal Errors- Machine calibration ErrorThe percentage error can be calculated as:%error=Experimental value-Correct Value/Correct value *1002. List all of the physical quantities that affect the value of centripetal force.Physical quantities that will affect centripetal force are mass, velocity, and radius.3. How did the period of rotation vary as you changed the radius?There is a positive relationship between the period of rotation and the radius, when one deceases so does the other. 4. Draw a circle to represent the path taken by your rotating mass. Place a dot on the circle to represent your rotating washer. Add a straight line from the dot to the center of the circle, representing the radius of rotation (the string). Now label the direction of the tangential velocity and the centripetal force.© 2014 eScience Labs, LLC.All Rights Reserved5. Refer to the picture in Figure 3 again (pictured to theright). Before the apparatus begins to spin the wiresconnecting the swings to the top of the structurewill be completely vertical. Once the apparatusbegins to spin the swings move outward radially, butalso upwards vertically. From where does the forcecausing this vertical acceleration come?The vertical force acts along the rope and the tensioncreated during centripetal force is called force tension. ThisTension cancels out the force due to gravity and the radialforce. © 2014 eScience Labs, LLC.All Rights Reserved Figure 3: Swings at an amusement parkexhibit a circular path of motion
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