uDu Hooke’s Law: Part 1 Objectives: Figure out the formula for Hooke’s Law relating the force of extension F to the amount of extension Δy of a spring. Calculate the “spring constant” for spring. You’ll need obsessively precise graphical methods to do so, and your answer must agree with mine within 1%. Equipment: Stand with spring-suspended hanger & mirrored scale; slotted weight set. Method: You’re on your own … this is a true “uDu”. Just don’t use a mass greater than 400g.

uDu Hooke’s Law: Part 1 And, in honor of Robert Hooke, all communications must be in bad English accents.

uDu Hooke’s Law: Part 2 Objectives: Demonstrate the (approximate) conservation of potential and kinetic energy in an oscillating system using the spring from Part 1. Additional Equipment: Motion sensor & data logger, ring stand & clamp set up as shown.

uDu Hooke’s Law: Part 2 Pre-Lab … F vs y plot Equilibrium position Graphical calculation of work Formulas

uDu Hooke’s Law: Part 2 Method: Use Logger Pro and the motion sensor to measure the position and velocity of the bobbing mass as follows: Set up data collection for 5 sec at samples per second. Start the mass bobbing from a moderate amplitude, let it settle a bit, then start the data collection. Discard trials with too much swinging motion. Use the curve fit function to fit a sine wave to about five or so cycles of both the “Position” and “Velocity” graphs. The amplitude “A” of the former gives the displacement Δy, and the amplitude of the latter gives the peak velocity.

uDu Hooke’s Law: Part 2 Analysis: From our pre-lab, you know how to calculate the change in PE from the equilibrium position by the work done, and how to calculate the maximum kinetic energy:

uDu Hooke’s Law: Part 2 Questions: Describe the transformation of potential and kinetic energy for a typical cycle of the pendulum in the context of energy conservation. Use the data cursor to compare the peaks and valleys of the position and velocity graphs. Describe the relation, and why you expect it based on your previous answer. Calculate the percent difference between the potential and kinetic energy. Does that represent an energy loss or an error in measurement or calculation? Explain.