Physics Sound Stations Lab Day 2 To be completed in your lab notebook Pre Lab: 1. As a child you pump your legs to gain height while swinging. Discuss with your group and explain why this increases your energy (both gravitational potential energy and kinetic energy) without someone else doing work on you by pushing you. 2. What is the amplitude of a mechanical wave an indicator of? (hint: think about an ocean wave) What is the common name for a sound wave’s amplitude? Procedure: There are several stations in this lab that each group will rotate through. The order of your lab may be different. Each time you come to a new station you should write the title of the station and answer any questions about that station underneath it. Be sure that your observations are clear, written in complete sentences and fully explain the observation you made! Music Box  You have several music boxes at your station, including one in and out of its box. Wind up the one inside the box and while holding it off the table listen to the music made. Take note of the volume.  Wind up the music box that is not contained in the box and while holding it off the table listen to the music made. Take note of the volume.  Now hold the music box that is not inside a box against the table and listen to the music made. Now press the music box against a cabinet, try a book or a desk, etc. Questions: 1. Why does the music box inside the box sound different than outside the box when held aloft? 2. Why does the music box inside the box sound louder when pressed against a desk or cabinet, etc.? Breaking Glass  Watch the videos about breaking glass shown to you in order to answer these questions. Questions: 1. As seen under the strobe light what is the glass doing before it breaks? What is making it do this? 2. Is it a high frequency or low frequency that breaks the glass? How can you tell on the strobe video? 3. Why are most people not able to break glass without the assistance of an amplifier? Boomwhackers  Boomwhackers create distinct tones when whacked against a surface. The tone is determined by the length of the tube.  Whack two different length tubes. Whack each boomwhacker in turn to determine the correlation between length and frequency.  Hum loudly over the end of a tube near and at its natural frequency (you may need to vary the frequency of your hum). The boomwhackers natural frequency is the frequency that makes a much louder sound than others. Answer question #3 below. Questions: 1. How do the lengths of the Boomwhackers compare in terms of their frequencies? 2. Did the Boomwhacker vibrate the whole time as you were varying the frequency you hummed over it, or at specific times? Explain your answer in detail and be sure to address the “why”.

Resonance Boxes  Carefully strike a tuning form on the mallet (black triangle on the table) and observe it. Note that its frequency is marked near the handle. You can stop the tuning fork by gently putting your hand on it.  There are two tuning forks attached to boxes that can be started with a soft mallet on a handle. With the boxes far from each other strike one tuning fork and listen. Note the volume.  Now with the open end of the boxes facing each other strike one tuning fork to start it and listen. Note the volume.  While the sound is still being made stop the tuning fork you started by gently putting your hand on it. Listen.  Place the small object on the second tuning fork and repeat the experiment. Questions: 1. What changed about the sound you heard when you struck the tuning fork that was attached to the wooden box instead of on its own? 2. What happened to the second tuning fork when the open side of the boxes were facing each other? Why does this happen? Explain your answer. 3. Why doesn’t the second tuning fork move when the small object is placed on it? Spouting Bowl  The metal bowl should be filled halfway with water and placed on a piece of foam.  Wash your hands and remove any rings you are wearing. Dip your hands into the bowl of water to wet them and rub your palms along the brass handles. It often works best to rub against the handle along the arrow shown at the right.  Try to produce a constant wave that creates splashes in the bowl at specific points.  Have different people try the bowl and try to create different amounts of “splashes.” Questions: 1. What have you produced in the bowl that appears to make it vibrate in sections? 2. What part of the standing wave are the splashes? Explain your reasoning. 3. What do you notice about the sound produce when you were able to create more points that splashed? Rings  Notice that there are different sized rings attached to one piece of cardboard.  Shake the cardboard back and forth side to side (as in the picture on the left) starting with low frequencies and gradually increasing. Note which rings seem to vibrate more than others at low or high frequencies.  Try to vibrate the rings by moving the piece of cardboard up and down (as shown in the picture on the right). Questions: 1. Did the biggest ring vibrate the most with high or low frequencies? Did the smallest ring vibrate the most with high or low frequencies? 2. Do you think you would be able to get the biggest ring to vibrate again at a different frequency? Explain why or why not.

Golf Balls  Notice that there are four different length dowels with a golf ball on the end of each. Shake the platform side to side at a low frequency and note which ball seems to vibrate more than the others.  Gradually increase the frequency. Note which ball seems to vibrate more than others at low or high frequencies.  Try to get the ball on the longest dowel to vibrate a second time. Questions: 1. Did the ball on the longest dowel vibrate the most with high or low frequencies? Did the ball on the shortest length dowel vibrate the most with high or low frequencies? 2. In order to get the ball on the end of the longest dowel to vibrate a second time what did you have to do? Why? Head Massager  This should not be brought near anyone’s head, it has not been cleaned!  Notice that there are two different lengths for the prongs of the head massager.  Gently pluck one of the long prongs and observe how it and any others move.  Stop the prongs from vibrating. Gently pluck one of the short prongs and observe how it and any others move.  Give the massager a quick shake in the air, like you were trying to flick some water off of it, and observe. Questions: 1. When the long prongs vibrated why didn’t the short ones? 2. When you shook the massager which prongs (long or short) vibrated? Why? 3. Do the short prongs vibrate at a higher or lower frequency than the long prongs? How do you know?