Sound Waves

1. Picture a long row of standing dominos, one a little behind the other so that knocking over the first will knock over the second and so on. Now imagine an idealized tube an inch or two in diameter extending from New York to California. Suppose this tube is filled with greased, essentially frictionless marbles and you push one more in at the East Coast end only to have one pop out at the West Coast end. What's happening, and how do these arrangements of dominos and marbles related to sound waves? 2. In December 1916, a major diaster befell a contingent of the Austrian army in the Alps fighting in Wourld War I. Almost as soon as they began a cannon barrage, an avalanche of snow came roar... click for more

Sound Waves

The ear has a protective overload mechanism called the "acoustic reflex". A sound in excess of about 85 dB causes muscles attached to the eardrum and ossicles to engage, which provides a safety margin of about 20 dB or 30 dB (the equivalent of ear plugs). This reflex takes about 30 ms to 40 ms to cut in, and maximum effect only occurs after about 150 ms. Why do many hunters show loss of hearing (especially in the right ear)? 2. Suppose you sing or yell into an open piano with its dampers lifted off the strings. You are likely to hear the instrument "speak" back in response. Explain. Imagine that you have two identical tuning forks and you tap one and then place it near the other. What, i... click for more

Electrostatics: Forces

Multiple choice: 1. If the charge on each two identical tiny spheres is doubled while their seperation is also doubled, their force of interaction will: (a) double (b) become halved (c) be quartered (d) stay unchanged (e) none of these. Explain your choice. 2. The E-field of a point-charge 4.0 m awya is measured to be 100 N/C. The field 2.0 m awya fromtht charge is: (a) 400 N/C (b) 50 N/C (c) 100 N/C (d) 800 N/C (e) none of these. Explain your choice 3. An electron inan electric field of 100 N/C experiences a force of: (a) 1.6 x 10^-10N (b) 1.6 x 10^-21N (c) 3.2 x 10^17N (d) 1.6 x 10^-17N (e) none of these. Explain your choice. Problem 1. A very small conducting sphere in air ca... click for more

Electrostatics: Forces

Problem 1. Determine the electric force acting on an electron placed in a uniform north-to-south E-field of 8.0 x 10^4 N/C in vacuum. 2. A +10-uC test-charge at some point beyond a charged sphere experiences an attractive force of 40 uN. Please coompute the value of the E-field of the sphere at that point in a vacuum. 3. Two point-charges of +10 nC and -20 nC lie on the x-axis at point x = 0 and x = +10, respectively. Find the electric field on the axis at point x = +5.0m. Assume vacuum. 4. Part I. Positive point-charges of +20 uC are fixed at two of the vertices of an equilaterial triangle with sides of 2.0 m, located in vacuum. Determine the magnitude of the E-field at the thir... click for more

Translational Equilibrium and Friction

There is a 200lb wieght on a table. attached to the mass is a string with the other end attached to a wall. hanging from the string is another string with the other end of that string attached to a unknow wieght. the string between the 200 lb mass and the wall form the following angles: from wall 70 degrees South West, and from the mass 0 degrees.. I need to find the maximum wieght that can be hung on the second string without upsetting equilibrium. Assumed that the coefficient of static friction is 0.3 between the 200 lbs mass and the table.