Experiment 1 Balancing Centripetal Force In this experiment you will investigate how the magnitude of radius affects the time period of an object with circular motion Materials 1 Aluminum Tube 1 m Fishing Line 5 Metal Washers Permanent Marker Scissors Stopwatch Tape Measure Procedure 1 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 point on 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 Data Radius Time per 15 Period s Expected 2014 eScience Labs LLC All Rights Reserved Percent m revolutions s 0 25 7 78 52 502 3 18 0 40 9 24 62 634 2 83 0 15 5 37 36 388 7 73 Value Error Post Lab Questions 1 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 Error The percentage error can be calculated as error Experimental value Correct Value Correct value 100 2 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 Reserved 5 Refer to the picture in Figure 3 again pictured to the right Before the apparatus begins to spin the wires connecting the swings to the top of the structure will be completely vertical Once the apparatus begins to spin the swings move outward radially but also upwards vertically From where does the force causing this vertical acceleration come The vertical force acts along the rope and the tension created during centripetal force is called force tension This Tension cancels out the force due to gravity and the radial Figure 3 Swings at an amusement park force exhibit a circular path of motion white line 2014 eScience Labs LLC All Rights Reserved
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