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 otherend through the tube. Tie four washers at the other end in agroup (Figure 6). 3. Measure 0.25 m from the single washer and use a permanentmark to mark this point on the line. 4. Hold the tube vertically at arm's length to your side so that thewasher near the mark is hanging from the top. 5. Hold a stopwatch in your other hand or get a willing participantto help you make time measurements. 6. Begin swinging the tube so that the top washer rotates in acircle. 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. © 2014 eScience Labs, LLC.All Rights Reserved Figure 6:Experiment set up.Table 1: Rotational DataRadius(m)Time per 15revolutions (s)Period (s)ExpectedValuePercentError (%)0.25 5.97 0.398 0.50 22%0.40 6.55 0.436 0.63 30%0.15 4.57 0.304 0.39 21%Post-Lab Questions1. Compare your measured data to your predicted values with a percent error calculation. Explain any differences with an error analysis.2. List all of the physical quantities that affect the value of centripetal force.3. How did the period of rotation vary as you changed the radius?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.5. 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?© 2014 eScience Labs, LLC.All Rights Reserved Figure 3: Swings at an amusement parkexhibit a circular path of motion
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