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Unformatted text preview: Lab Section: ______ Name: ANSWERS Lab Instructor: ___________________ Instructors Signature: __________________ P2207 Lab Working Notes Questions 6-1 Cornell University, Fall 2010 Lab 6 - Energy Conservation in Oscillating Systems and for a Bouncing Ball This is a revised and condensed version of Labs 5 and 6 in your lab manual. All the instructions you need to do the lab are right here on this yellow sheet. Please attach copies of your graphs from Logger Pro. 1. Bowling Ball Pendulum Experiment This experiment is done with all the students and the TA working together. A massive bowling ball is hanging by a cable from a hook in the ceiling. The Ranger can be set to monitor the balls horizontal position, x . The TA will open Logger Pro using the alias Pendulum I 2010. You will see a 2-graph layout of position vs. time and velocity vs. time. Zero the Ranger so that it reads x = 0 when the pendulum is hanging perfectly still. Then set the ball swinging with an amplitude of about 10 cm, and record the oscillations. Take a good look at the graphs of x(t) and v x (t) : both swing symmetrically about zero. Q : Are their periods of oscillation the same? YES NO Q : Is v x (t) a maximum at the same time as x(t) ? (A one-word answer will NOT suffice here! Give some detail.) No, v x (t) is zero when x(t) is maximum, and vice versa. Quit Logger Pro and re-open it using the alias Pendulum II 2010 to obtain a 5-graph layout of position, velocity, kinetic energy, potential energy, and the sum of those energies. We need to enter some parameters into Logger Pro, so that it can calculate those energy graphs. The gravitational potential energy of the pendulum is U(t) = W L [x(t)] 2 , where W is the weight of the pendulum, and L is the distance from the support at the ceiling to the center of the bowling ball. (This formula can only be used for small-amplitude oscillations - see your lab manual for details.) The kinetic energy of the pendulum is K = m [v(t)] 2 , where m is the mass of the pendulum and v(t) is its velocity. P2207 Lab Working Notes Questions 6-2 Cornell University, Fall 2010 We need to obtain W, m and L , and enter their values into Logger Pro. We measured the weight W of the bowling ball in Lab 2: W = 62.5 N. The mass m is then given by m = W g = 62.5 N 9.81 m/s 2 = 6.37 kg. Now measure the length L , remembering to measure to the center of the bowling ball. L = 2.32 m. The TA will enter the above values of W, m and L into the energy formulae in Logger Pro. Now we'll record some oscillations of the pendulum, the energy graphs will be created in real- time. The TA will print out a copy of the graphs for every student. [Please print p.1 only!] 2. Cart-On-Spring Experiment This experiment is done with all the students and the TA working together....
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