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 ...continues

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 ...continues

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/ ...continues

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 ...continues

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 ...continues

Working with heat and matter.

1. How much heat is required to raise the temperature by 10 degrees Celsius of one kg of water and iron? 2. Two identical objects (the same mass, material) at temperatures T1 = 20 degrees and T2 = 30 degrees are in contact. What is the final temperature of these objects after they reach thermal equilibrium?

First year physics

Qn 3. The transfer of heat from the body's interior to the surface is achieved primarily through the flow of blood. In cold surroundings blood flow near the skin is reduced by constriction of capillaries. This allows the skin to provide the insulation. Skin temperature can drop to as low as 15 degrees reducing the heat loss f ...continues

Direct Currents

1. What happens when you turn the key in the ignition of your automobile? Should you start your car on a cold rainy night with the wipers, lights, heater and defroster all on? Explain. 2.Take an ordinary metal-body flashlight. Explain how it works and discuss the significance of the arrangement of the dry cells. 3.High vol ...continues

Direct Currents

Multiple Choice 1. The resistance of a superconducting material drops, essentially to zero, rather suddenly when: (a) the sample is heated above Tc (b) the sample is exposed to a magnetic field (c) the sample is cooled below Tc (d) the sample experiences a current Ic (e) none of these. Explain your choice. 2. Imagine a len ...continues

Circuits

Multiple choice: 1. An ideal source of emf is connected in seriew with a resistor in closed loop, and a current or 0.e50 A circulates. An additional 6.0-Ohm resistor is added in series, and the current drops to 0.30 A. The original resistance was: (a) 9.0 Ohm (b) 6.0 Ohm (c) 15 Ohm (d) 3.0 Ohm (e) none of these. Explain your ch ...continues