# PHYS310 Lab 13 Uniform Circular Motion

*Tutorial includes complete laboratory (including methods and materials, experimental data, full explanations, and diagrams) with the following questions answered:*

Lab Exercise

Experiment 1: Balancing the Centripetal Force

Table 1: Period data for revolving washer with variable radius

Questions

1. If you suddenly cut the string connected to your rotating mass, what would be the direction of its velocity? Draw a diagram showing the direction of motion of an object just cut from a circular revolution.

2. How did the period of revolution change to account for a larger and smaller radius? How did the angular frequency change?

3. 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, centripetal force, and the centrifugal “force.”

4. Use your data to find the average period for each radius. Use this and the rest of your data to calculate a) the average velocity of your spinning mass, b) its angular velocity in rad/sec, and c) the centripetal acceleration for each radius.

5. How is the centripetal force on the revolving washer related to the force of gravity on the hanging washers? Write an expression that equates the centripetal force Fc of the rotating mass to the force of gravity on the hanging mass. Write your expression in terms of m1 (revolving mass), m2 (hanging mass), T, R, and g.

6. What do you notice about your centripetal acceleration values in Question 4? Explain this result knowing the relationship between centripetal acceleration and centripetal force, given the experimental constant 4m1 = m2.

7. Solve your expression above for the period T in terms of R and g.

8. Plug in your radius values into this equation to find the expected frequency of rotation. Record these values in the table above. Were your experimental values close? How could you improve the experiment to reduce error?

9. Use the rotational kinematics equations to calculate the angular acceleration necessary to increase the angular velocity of your spinning mass from 10 rad/s to 20 rad/s in a time of 8 seconds.

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