PHYS 202 Laboratory #4. Activity 1: Thinking about Oscillating Systems

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1 SHM Lab 1 Introduction PHYS 202 Laboratory #4 Oscillations and Simple Harmonic Motion In this laboratory, we examine three simple oscillatory systems: a mass on a spring, a pendulum, and a mass on a rubber band. Activity 1: Thinking about Oscillating Systems Let s begin a study of oscillations with a simple everyday observation. A mass on a spring will oscillate, a pendulum will oscillate, a mass on a rubber band will oscillate. List 5 other oscillating systems Oscillating systems which repeat are called. If the earth day was 18 hours, 150 million years ago, and it is 24 hours now, how long wil an earth day be 1 million years from now? Activity 2: Measuring Spring Constant Pick a spring out of the spring box, and measure it s spring constant. One way to do this is to hang vertical weights, and measure the displacement. Do this, and make a table such as the one below. After your first measurement, do a quick calculation of the spring constant. If the spring constant is greater than 10 N/m, choose a less stiff spring out of the box. An easy way to do these measurements is to measure the distance from the tabletop to the bottom of your spring. Then you can make measurements of displacement (with different masses) from the tabletop. The difference between these measurements is the distance the spring has stretched.

2 SHM Lab 2 to bottom of spring equilibrium Discuss 2 other methods that could be used to measure the spring constant: Method 1: Method 2: Make a plot of Force vs. Displacement, and put it here. Make sure the Displacement is on the x-axis. Questions/Other Activities 1. What is the slope of the above graph? (Be sure to include units.) If the plot is not exactly linear, use a linear curve fit. 2. What weight should you add to make the period 1 second? Add that weight and confirm your calculations. (you may need to use a period of 2 seconds, depending on the stiffness of your spring).

3 SHM Lab 3 3. What length should you make a pendulum so that it will have the same 2 second period? Do it, confirm your calculations. 4. Get your pendulum and your spring to oscillate in phase with each other, show your instructor, and have him/her sign you lab book. Activity 3: Spring Constant of a Rubber Band? Repeat Activity 2 for a rubber band. to bottom of spring equilibrium Questions/Other Activities 1. What is the slope of the above graph? (Be sure to include units.) If the plot is not exactly linear, what function best describes. Activity 4: Spring Constant of Spring Combinations? Repeat Activity 2 for a second spring.

4 SHM Lab 4 to bottom of spring equilibrium Repeat Activity 2 for your two springs in parallel. to bottom of spring equilibrium Repeat Activity 2 for your two springs in series, i.e. when one spring is attached to another.

5 SHM Lab 5 to bottom of spring equilibrium Questions/Other Activities 1. What is the effective spring constant of the two springs when they are connected in series? Use a physics textbook or an internet search engine to determine a theoretical formula for the effective spring constant of two springs connected in series. Compare your answers. 2. What is the effective spring constant of the two springs when they are connected in parallel? Use a physics textbook or an internet search engine to determine a theoretical formula for the effective spring constant of two springs connected in parallel. Compare your answers. (Extra Credit) Activity 5: Spring Constant a Physical Pendulum? Repeat Activity 2 for a meter stick (with holes).

6 SHM Lab 6 to bottom of spring equilibrium 1. Whatistheeffectivespringconstantoftheruler? Useaphysicstextbookoraninternet search engine to determine a theoretical formula for the effective spring constant of the ruler. Compare your answers.