Fundamentals of Physics Exam 4 | Questions and Answers

Fundamentals of Physics Exam 4 | Questions and Answers Sonar is a technology used to make maps of the sea floor, as well as to find fish and military targets. Sonar is very similar to medical ultrasound, in that it makes images using sound, but the sonar device is attached to the bottom of a boat and projects downward through the water. While medical ultrasound uses frequencies in the MHz, sonar works best with lower frequencies, because it has to travel longer distances. Calculate the wavelength of a sonar wave with a frequency of 100 kHz. The speed of sound in water is 1500 m/s. 15 mm All electromagnetic radiation has a speed of c = 3 x 108 m/s. What is the frequency of a green laser having a wavelength of 500 nm? (Answer in THz) 600 THz If a car that is moving away from you blows its horn, the frequency you hear will be ________ what the driver hears. a. higher than b. lower than c. the same as d. the inverse of A sound wave has a speed of 340 m/s and a frequency of 1000 Hz. The period of the sound is closest to ________ms. 1 ms Regular water waves that we see on the beach are an example of ________ waves. a. longitudinal b. standing c. doppler shifted d. transverse The speed of sound in water is _________ than in air. Faster The energy in a sound wave is mostly closely related to the ________ of the sound. a. frequency b. wavelength c. wave speed d. amplitude As humans age, they naturally lose sensitivity to ________ sounds. a. longer wavelength b. lower frequency c. higher frequency d. higher amplitude The normally quoted frequency range of healthy human hearing is ________. a. 20 Hz - 20 kHz b. 20 Hz - 200 KHz c. 20 Hz - 2kHz d. 20 Hz - 2000 Hz 85 decibels= begin hearing damage Dolphins and other marine mammals use ________ to communicate and navigate. ultrasound - sound composed of frequencies above the range of human hearing The parameter of a sound wave that is perceived as pitch is the ________. a. frequency b. wave speed c. wave shape d. amp The parameter of a sound wave that is heard as loudness is the ________. a. wave shape b. wavelength c. frequency d. intensity The parameter of a sound wave that lets you identify voices and musical instruments is the ________. a. amplitude b. frequency c. wave shape d. wavelength Compared to a 90 dB sound, the intensity of a 40 dB sound is ________. 100,000 times lower Smaller musical instruments tend to make ________ sounds than larger musical instruments. a. lower frequency b. lower wave speed c. higher frequency d. larger amplitude In a copper wire, the particles that actually move and carry the electrical energy are the ________. Electrons The standard unit for electrical potential is the ________. Volt Semiconductors are useful in electronics because ________. a. their conductivities can be controlled b. their conductivities are extremely low c. they store charge extremely well d. their conductivities are extremely high In materials that are good conductors of electricity, ________. a. some of the neutrons are loosely attracted to the protons b. some of the protons are loosely attracted to the nucleus c. the ions are mostly isotopes d. some of the electrons are loosely attracted to the nucleus Higher voltage means ________. a. higher current density per coulomb b. higher charge per coulomb c. higher energy per coulomb d. more electrons per coulomb Batteries and solar cells produce ________ electrical power. a. sine wave b. direct current c. alternating current d. inverted current If you attach a 12 volt battery to a 1000 ohm resistor, the current will be ________. a. 240 A b. 12 kA c. 12,000 mA d. 12 mA In the US, electrical power is delivered to your home at 120 volts AC. If you plug in a 600 W bread maker, the current it will draw will be about ________. 5A The wires powering a 24 kW heating unit can carry a maximum of 100 A. What is the minimum voltage required? 240 V Electric current always involves ________. a. a changing electrical resistance b. the flow of electric voltage c. the flow of electric charge d. a steady electrical resistance The fundamental source of most magnetic forces is ________. a. moving magnetic domains b. the movement of magnetic monopoles c. electric current d. Earth's magnetic field. moving charges produce a magnetic field Which of the following statements is always true? a. Unlike magnetic poles repel like magnetic poles. b. Like magnetic poles repel unlike magnetic poles. c. Like magnetic poles repel, unlike magnetic poles attract. d. Magnetic monopoles do not repel or attract. Electric motors normally work via ________. a. magnetic currents acting on electric forces b. electromagnetic currents flowing between the wires and the magnets c. magnetic wires spinning in a loop d. magnetic forces acting on electric currents The best way to create an electromagnet is to ________. a. turn a magnetic wire in an electric field b. spin a magnet near a coil of wire c. run electric current through a coil of wire d. spin a coil of wire near a magnet Earth's magnetic field is particularly beneficial to humans because ________. a. it is primarily responsible for rainbows b. it deflects incoming charged cosmic radiation c. it attracts water molecules d. it helps hold the atmosphere close to Earth's surface An electric generator normally consists of _______. a. loops of wire rotating in a magnetic field b. rotating electric and magnetic fields c. rotating magnets in an electric field d. two transformers back to back Transformers make the distribution of electrical power more efficient by ________. a. increasing the heat dissipation in the distribution wires b. allowing less current to flow through distribution wires c. adjusting to Earth's magnetic field. d. allowing more current to flow through distribution wires Changing the number of primary or secondary turns in a transformer ________. a. changes the voltages b. changes the voltages and the currents c. changes the currents d. changes the voltages, the currents and the power Generators naturally produce DC, but it can easily be converted to AC. true or false False Whether you're talking about a motor, a generator or a transformer, power is always ________. a. the rate of current flow b. the rate of voltage changing c. the magnetic field times the electric field d. the rate of energy flow sine curve The waveform traced by simple harmonic motion, which can be made visible on a moving conveyor belt by a pendulum swinging at right angles above the moving belt. amplitude for a wave of vibration, the max displacement on either side of the equilibrium position. wavelength the distance between successive crests, troughs, or identical parts of a wave. frequency for a vibrating body or medium, the number of vibes per unit time. For a wave, the number of crests that pass a particular point per unit time. # vibes / seconds SI unit is Hertz 1 Hz= 1 vibe / s period the time for one complete vibration P= 1/ frequency frequency = 1/ period transverse wave the medium vibrates perpendicularly (at right angles) to the direction in which the wave travels. Light waves, waves on stringed instrument, waves at the beach are examples. sideways longitudinal waves a wave in which the medium vibrates parallel to (along) the direction in whch the wave travels. sound waves are an ex. wave speed speed with which a wave passes a particular point. wave speed = frequency x wavelength wave speed also = wavelength/period sound travels slowest in gas, fastest in solid, mediumest in liquid increase temperature increase speed of sound sound speed depends on wind conditions, temperature, and air humidity. Does not depend on loudness or frequency of sound wave interference the phenomenon that occurs when two waves meet while traveling along the same medium