Experiment 5: Centripetal Force Equipment: "A" base, rotating platform with centripetal force accessory, hooked mass, stopwatch, and hanging masses Objective: To study centripetal force by comparing the tension in a spring as found dynamically (from the centripetal force) with that obtained statically. Theory: When an object of mass M, attached to a string r, is rotated in a horizontal circle, the centripetal force on the mass is given by: F MV where vis the tangential velocity. To measure the velocity, the time for one rotation (the period, 7) is measured. Then: T and the centripetal force is given by: 4 TT 2Mr F = T2 Leveling the base and rotating platform If the platform is not level, the uneven performance will affect the results. To level the apparatus, perform the following steps. 1. Purposely make the apparatus unbalanced by attaching the 300g square mass onto either end of the aluminum track. Tighten the screw so the mass will not slide. If the hooked mass is hanging from the side post , place the square mass on the same side. 2. Adjust the leveling screw on one of the legs of the base until the end of the track with the square mass is aligned over the leveling screw on the other leg of the base. 3. Rotate the track 90 degrees so it is parallel to one side of the "A" and adjust the other leveling screw until the track will stay in this position. 4. The track is now level and is should remain at rest regardless of its orientation. 5. Remove the 300g square mass.5. Data Tables with titles and columns/rows labeled with quantity and dimensions. Accuracy /uncertainties. 6. Analysis / Calculations Any formula and or calculations. Uncertainty calculation of results. Graphs. 7. Conclusions Always discuss your final measurement with uncertainty and how it differs from the expected value.string side post center post assembly assembly clamp-on rotating pulley platform hanging "A" base mass side post center post spring bracket plastic indicator disk indicator bracket mass pulley rotating reference mark platform (center of post) thread zero mark of rule2. Purpose (Brief, concise!) 3. Apparatus 4. Procedure Describe briefly how you carried out the experiment. The procedure SHOULD NOT be a copy of the written procedure in the lab document. It SHOULD be a summary of important steps only. 5. Data Tables with titles and columns/rows labeled with quantity and dimensions. Accuracy luncertainties. 6. Analysis I Calculations Analysis: 1. The weight of the mass hanging over the pulley is equal to the centripetal force applied by the spring. Calculate the force F = mg . 2. Calculate the centripetal force (using the average period for 7) from the equation below. 4 TT 2 Mr F = T2 3. Calculate the percent difference between the two values found for the centripetal force. 4. Briefly discuss possible sources of error.meeting rotating platform platform (rotated 90' as shown) "A" base 300g square mass 300g square adjust this foot then adjust this mass eveling first foot Procedure: 1. Hang the object from the side post and connect the string from the spring to the object. The string must pass under the pulley on the center post. 2. Set the side post at 20 cm. This is the radius r. 3. Attach the pulley to the end of the track nearer to the hanging object. Attach a string to the hanging object and hang masses over the pulley until the object hangs vertically. Record this mass in table 1. 4. Align the indicator bracket on the center post with the orange indicator. 5. Remove the mass that is hanging over the pulley and remove the pulley. 6. Rotate the apparatus by turning the shaft, increasing the speed until the orange indicator is centered in the indicator bracket on the center post. This indicates that the string supporting the hanging object is once again vertical and thus the hanging object is at the desired radius. 7. Maintaining this speed, use a stopwatch to time ten revolutions. Divide the time by ten and record the period in table 1. 8. Calculate the average period and record in table 1. Table 1 Mass of the object M = 106 grams Mass hanging over the pulley m = 7 79 Radius Period 20 cm 20 cm to sec 20 cm average period = 3.75