# Physica Lab

Suellen Fonseca Physics 151 April 3, 2013 Questions and Answers: 1. Define uniform circular motion. ? A. Is an object in uniform circular motion accelerating? ? B. Define centripetal acceleration, and state its magnitude and direction. (2. 0 points) Ans: An object moving at a constant velocity around a circular path is performing a uniform circular motion. The object’s path is considered to be tangent to the circle due to the fact that it is constantly changing position as it goes around the circle.
Therefore the velocity would also be tangent to the circle. [A] The object in uniform circular motion is experiencing acceleration due to the fact that is it changing direction constantly. [B] This is the centripetal acceleration. It’s directed towards the center of rotation. Is magnitude is calculated by V2r where v is the tangential velocity and r is the radius of rotation 2. A car is driven around a circular track. Which would have a greater effect on the magnitude of its acceleration, doubling the speed or moving to a track with half the radius?
Please show your proof or calculations. (1. 0 point) A. Define centripetal force (F c) ? B. Which object is providing the centripetal force in this experiment? Ans: Cense acceleration is given by V2r doubling the velocity has a greater effect then dividing the radius by 2. [A] The force the supply the acceleration is called centripetal force. This force is also always directed towards the center of rotation. [B] The object providing the centrifugal force in this experiment is the tention in the rope. 3.

When you go around a corner in a car, do you feel centripetal or centrifugal (Fg) force ? acting upon you? (1. 5 points) Ans: The car is experiencing centripetal force thus it does not “fly of “ the streat. 4. Explain why ? F=mg? =? Fc=4? 2 M f 2 r? in our experiment. (0. 5 point) Ans: It worked because the balancing force is the tetion In the string which allows the wheight to move in a circle. 5. List the data and sample calculations obtained in lab. (0. 5 point) | r (meter) | m (kg)| f (sec^-1)| a_c = 4(? ^2)(f^2)r (m/s^2)| F_c = mg (N)| 1| 0. 49| 0. 4| 1. 271| 9. 502| 3. 92| 2| 0. 16| 0. 45| 1. 348| 11. 478| 4. 41| 3| 0. 175| 0. 55| 1. 416| 13. 852| 5. 39| 4| 0. 197| 0. 79| 1. 608| 20. 109| 7. 742| 6. Plot the graph of Fc vs. ac . A. What is the expected slope of the line graphed (and explain why you expect this result)? B. Calculate the actual slope of best fit line. Also calculate the percent error for the slope, and ? state and explain the sources of error. (4. 5 points) [A] the expected slope id 0. 4 [B] the actual slope from the best fit line is 0. 106. One sores of errow would be the timing of the number of revolutions. An erro on the radius mesurament | Uncertainty| Slope| ±0. 01522| y-intercept| ±0. 2177| 7. What do you expect the y-intercept of the line from question 6 to be? Find the actual y-intercept for your best fit line. (show calculations) (1. 0 point) 8. Imagine that a much harder spring (spring with higher spring constant k) is used in the experiment. Explain how the centripetal force F c and the period f of the hanging mass will change. i. e. if they will increase or decrease) (1. 0 point) Ans: If we had a harder spring the frequency would be bigger therefore the centripetal force would also be bigger. Conclusion: In this lab we were trying to prove that fc=mg. according to my calculations the results were close but not perfect. This can be because of lost of energy due to friction or simply error in calculations. As predicted every time there was a change in radius or the frequency the centripetal force changed.

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