Physics 1310 Conceptual QA

What determines the period of a mass–spring oscillator? (Simple Harmonic Motion)

T=2πm/k. Depends on mass and spring constant only.

T=2πL/g. Depends on length and gravity only. (Simple Harmonic Motion)

v = 0, a = maximum.

At equilibrium, what are v and a? (Simple Harmonic Motion)

v = maximum, a = 0.

Total energy of a spring oscillator? (Simple Harmonic Motion)

E=1/2kA2

Relationship between speed, frequency, wavelength? (Waves + Sound)

v=fλ

What happens to intensity when distance doubles?

Drops by factor of 4

What is the decibel formula?

β=10log⁡(I/I0)

Adding identical sound sources increases dB by how much?

Doubling → +3 dB

Condition for constructive interference?

Path difference = nλ

Condition for destructive interference?

Path difference = (n+1/2)λ

Fundamental wavelength for a string fixed at both ends?

λ=2L

Fundamental wavelength for a closed pipe?

λ=4L

Which harmonics exist in a closed pipe?

Only odd harmonics (1, 3, 5…)

When observer moves toward source, what happens to frequency?

Increases

Pressure at depth h?

P=P0+ρgh

Buoyant force formula

FB=ρVg

Fraction submerged for floating object?

ρobject/ρfluid

Continuity equation?

A1v1=A2v2

Bernoulli principle?

Higher speed → lower pressure

Newton’s law of gravitation?

F=G*m₁m₂/r²

Orbital speed?

v= square root( 2GM/r)

Escape speed?

v=2GM/r

Why does destructive interference occur when the two pulses overlap instead of constructive interference?

because a pulse is inverted upon reflection

As the pulses interfere destructively there is a point in time when the string is perfectly straight. Which of the following statements is true at this moment?

The string has only kinetic energy.

A certain sound contains the following frequencies: 400 Hz, 1600 Hz, and 2400 Hz. Select the best description of this sound.

This is a complex tone with a fundamental of 400 Hz, plus some of its overtones.

If you are 3.00 m from speaker A directly to your right and 3.50 m from speaker B directly to your left, will the sound that you hear be louder than the sound you would hear if only one speaker were in use?

yes

If the strings have different thicknesses, which of the following parameters, if any, will be different in the two strings?

wave speed and wave length

If the strings have the same thickness but different lengths, which of the following parameters, if any, will be different in the two strings?

none of the above

Archimedes' principle

Fbuoyant=ρfluidgV

The magnitude of the buoyant force is equal to the weight of fluid displaced by the object.

Under what circumstances is this statement true?

for every object submerged partially or completely in a fluid

The magnitude of the buoyant force is equal to the weight of the amount of fluid that has the same total volume as the object.

Under what circumstances is this statement true?

for an object completely submerged in a fluid

The magnitude of the buoyant force equals the weight of the object.

Under what circumstances is this statement true?

for an object that floats

The magnitude of the buoyant force is less than the weight of the object.

Under what circumstances is this statement true?

for an object that sinks

An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a denser liquid. What would you observe?

The object would float submerged less deeply than in the first container.

An object is floating in equilibrium on the surface of a liquid. The object is then removed and placed in another container, filled with a less dense liquid. What would you observe?

More than one of these outcomes is possible.

Two objects, T and B, have identical size and shape and have uniform density. They are carefully placed in a container filled with a liquid. Both objects float in equilibrium. Less of object T is submerged than of object B, which floats, fully submerged, closer to the bottom of the container. Which of the following statements is true?

Object B has a greater density than object T.

Traveling waves propagate with a fixed speed usually denoted as v (but sometimes c). The waves are called __________ if their waveform repeats every time interval T.

periodic

If the velocity of the wave remains constant, then as the frequency of the wave is increased, the wavelength __________.

decreases

The difference between the frequency f and the frequency ω is that f is measured in cycles per second or hertz (abbreviated Hz) whereas the units for ω are __________ per second.

radians

Having established that a sound wave corresponds to pressure fluctuations in the medium, what can you conclude about the direction in which such pressure fluctuations travel?

Pressure fluctuations travel along the direction of propagation of the sound wave.

Based on the information presented in the introduction of this problem, what is a sound wave?

Propagation of pressure fluctuations in a medium

Does air play a role in the propagation of the human voice from one end of a lecture hall to the other?

yes

A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that the amplitude of the pressure fluctuations is larger. In addition to the larger amplitude, what distinguishes the second sound from the first one?

It is perceived as louder.

A certain sound is recorded by a microphone. The same microphone then detects a second sound, which is identical to the first one except that it has twice the frequency. In addition to the higher frequency, what distinguishes the second sound from the first one?

It is perceived as higher in pitch

What varies between two tones that are different in timbre, that is, two tones that have the same fundamental frequency but are produced, say, by different musical instruments?

the harmonic content

The velocity of the source is positive if the source is ______________. Note that this equation may not use the sign convention you are accustomed to. Think about the physical situation before answering.

traveling away from the listener

The velocity of the source is measured with respect to the ________.

medium (such as air or water

The velocity of the listener is positive if the listener is _____________.

traveling toward the source

The velocity of the listener is measured with respect to the ________.

medium

Now, imagine that the source is to the left of the listener, so that the positive reference direction is in the −x direction. If the source is stationary, what value does fL approach as the listener's speed (moving in the +x direction) approaches the speed of sound?

0

Which of the following statements best describes the characteristic of the restoring force in the spring-mass system described in the introduction?

The restoring force is directly proportional to the displacement of the block.

The magnitude of the block's acceleration reaches its maximum value when the block is

at either its rightmost or leftmost position.

The speed of the block is zero when it is

at either its rightmost or leftmost position.

The speed of the block reaches its maximum value when the block is

in the equilibrium position.

What effect does dropping the sandbag out of the cart at the equilibrium position have on the amplitude of your oscillation?

It decreases the amplitude.

What effect does dropping the sandbag out of the cart at the equilibrium position have on the maximum speed of the cart?

It has no effect on the maximum speed.

What effect does dropping the sandbag at the cart’s maximum distance from equilibrium have on the amplitude of your oscillation?

It has no effect on the amplitude.

What effect does dropping the sandbag at the cart’s maximum distance from equilibrium have on the maximum speed of the cart?

It increases the maximum speed.

Where will the object's maximum acceleration first be attained?

release point

The gravitational field on the surface of the earth is stronger than that on the surface of the moon. If a rock is transported from the moon to the earth, which properties of the rock change?

weight only

An object is lifted from the surface of a spherical planet to an altitude equal to the radius of the planet. As a result, what happens to the mass and weight of the object?

mass remains the same; weight decreases

If Anya decides to make the star twice as massive, and not change the length of any crossbar or the location of any object, what does she have to do with the mass of the smiley face to keep the mobile in perfect balance? Note that she may have to change masses of other objects to keep the entire structure balanced.

make it twice as massive