ConcepTest 11.1aConcepTest 11.1a Harmonic Motion I

1) 01) 0

2) A/22) A/2

3) A3) A

4) 2A4) 2A

5) 4A5) 4A

A mass on a spring in SHM has

amplitude A and period T. What

is the total distance traveled by

the mass after a time interval T?

ConcepTest 11.1aConcepTest 11.1a Harmonic Motion I

1) 01) 0

2) A/22) A/2

3) A3) A

4) 2A4) 2A

5) 4A5) 4A

A mass on a spring in SHM has

amplitude A and period T. What

is the total distance traveled by

the mass after a time interval T?

In the time interval Ttime interval T (the period), the mass goes

through one complete oscillationcomplete oscillation back to the starting

point. The distance it covers is: A + A + A + A (4A).The distance it covers is: A + A + A + A (4A).

ConcepTest 11.2 ConcepTest 11.2 Speed and Acceleration

1) x = A

2) x > 0 but x < A

3) x = 0

4) x < 0

5) none of the above

A mass on a spring in SHM has

amplitude A and period T. At

what point in the motion is v = 0

and a = 0 simultaneously?

ConcepTest 11.2 ConcepTest 11.2 Speed and Acceleration

1) x = A

2) x > 0 but x < A

3) x = 0

4) x < 0

5) none of the above

A mass on a spring in SHM has

amplitude A and period T. At

what point in the motion is v = 0

and a = 0 simultaneously?

If both If both vv and and aa would be would be

zero at the same time, the zero at the same time, the

mass would be at rest and mass would be at rest and

stay at rest!stay at rest! Thus, there is

NO pointNO point at which both vv

and aa are both zero at the

same time.Follow-up:Follow-up: Where is acceleration a maximum? Where is acceleration a maximum?

A mass oscillates in simple

harmonic motion with amplitude

A. If the mass is doubled, but the

amplitude is not changed, what

will happen to the total energy of

the system?

1) total energy will increase

2) total energy will not change

3) total energy will decrease

ConcepTest 11.5aConcepTest 11.5a Energy in SHM I

A mass oscillates in simple

harmonic motion with amplitude

A. If the mass is doubled, but the

amplitude is not changed, what

will happen to the total energy of

the system?

1) total energy will increase

2) total energy will not change

3) total energy will decrease

The total energy is equal to the initial value of the

elastic potential energy, which is PEs = ½kA2. This

does not depend on mass, so a change in mass will not affect the energy of the system.

ConcepTest 11.5aConcepTest 11.5a Energy in SHM I

Follow-up:Follow-up: What happens if you double the amplitude? What happens if you double the amplitude?

A mass oscillates on a vertical

spring with period T. If the whole

setup is taken to the Moon, how

does the period change?

1) period will increase

2) period will not change

3) period will decrease

ConcepTest 11.7cConcepTest 11.7c Spring on the Moon

A mass oscillates on a vertical

spring with period T. If the whole

setup is taken to the Moon, how

does the period change?

1) period will increase

2) period will not change

3) period will decrease

The period of simple harmonic motion only depends on the mass and the spring constant, and does not depend on the acceleration due to gravity. By going to the Moon, the value of g has been reduced, but that does not affect the period of the oscillating mass-spring system.

ConcepTest 11.7cConcepTest 11.7c Spring on the Moon

Follow-up:Follow-up: Will the period be the same on any planet? Will the period be the same on any planet?

Two pendula have the

same length, but different

masses attached to the

string. How do their

periods compare?

1) period is greater for the greater mass

2) period is the same for both cases

3) period is greater for the smaller mass

ConcepTest 11.8aConcepTest 11.8a Period of a Pendulum I

Two pendula have the

same length, but different

masses attached to the

string. How do their

periods compare?

1) period is greater for the greater mass

2) period is the same for both cases

3) period is greater for the smaller mass

The period of a pendulum depends on the length and the acceleration due to gravity, but it does not depend on the mass of the bob.

T = 2T = 2((LL//gg))T = 2T = 2((LL//gg))

ConcepTest 11.8aConcepTest 11.8a Period of a Pendulum I

Follow-up:Follow-up: What happens if the amplitude is doubled? What happens if the amplitude is doubled?

A grandfather clock has a

weight at the bottom of the

pendulum that can be moved

up or down. If the clock is

running slow, what should

you do to adjust the time

properly?

1) move the weight up

2) move the weight down

3) moving the weight will not matter

4) call the repair man

ConcepTest 11.9 ConcepTest 11.9 Grandfather Clock

A grandfather clock has a

weight at the bottom of the

pendulum that can be moved

up or down. If the clock is

running slow, what should

you do to adjust the time

properly?

1) move the weight up

2) move the weight down

3) moving the weight will not matter

4) call the repair man

The period of the grandfather clock is too long, so we need to decrease the period (increase the frequency). To do this, the length must be decreased, so the adjustable weight should be moved up in order to shorten the pendulum length.

T = 2T = 2((LL//gg))T = 2T = 2((LL//gg))

ConcepTest 11.9 ConcepTest 11.9 Grandfather Clock

ConcepTest 11.15aConcepTest 11.15a Wave Motion IWave Motion I

Consider a wave on a string moving to the right, as shown below.

What is the direction of the velocity of a particle at the point labeled A ?

1)

2)

3)

4)

5) zero

A

ConcepTest 11.15aConcepTest 11.15a Wave Motion IWave Motion I

Consider a wave on a string moving to the right, as shown below.

What is the direction of the velocity of a particle at the point labeled A ?

1)

2)

3)

4)

5) zero

The velocity of an

oscillating particle

is (momentarilymomentarily) zerozero

at its maximum

displacement.

A

Follow-up:Follow-up: What is the acceleration of the particle at point A? What is the acceleration of the particle at point A?

Consider a wave on a string moving to the right, as shown below.

What is the direction of the velocity of a particle at the point labeled B ?

1)

2)

3)

4)

5) zero

B

ConcepTest 11.15bConcepTest 11.15b Wave Motion IIWave Motion II

Consider a wave on a string moving to the right, as shown below.

What is the direction of the velocity of a particle at the point labeled B ?

1)

2)

3)

4)

5) zero

The wave is moving

to the rightright, so the

particle at B has to

start moving upwardsmoving upwards

in the next instant of

time.

B

ConcepTest 11.15bConcepTest 11.15b Wave Motion IIWave Motion II

Follow-up:Follow-up: What is the acceleration of the particle at point B? What is the acceleration of the particle at point B?

ConcepTest 11.19aConcepTest 11.19a Standing Waves IStanding Waves IA string is clamped at both ends and plucked so it vibrates in a standing mode between two extreme positions a and b. Let upward motion correspond to positive velocities. When the string is in position b, the instantaneous velocity of points on the string:

a

b

1) is zero everywhere

2) is positive everywhere

3) is negative everywhere

4) depends on the position

along the string

Observe two points:

Just before b

Just after b

Both points change direction before and after b, so at b all points must have zero velocity.

ConcepTest 11.19aConcepTest 11.19a Standing Waves IStanding Waves IA string is clamped at both ends and plucked so it vibrates in a standing mode between two extreme positions a and b. Let upward motion correspond to positive velocities. When the string is in position b, the instantaneous velocity of points on the string:

1) is zero everywhere

2) is positive everywhere

3) is negative everywhere

4) depends on the position

along the string

a

b

c

ConcepTest 11.19bConcepTest 11.19b Standing Waves IIStanding Waves IIA string is clamped at both ends and plucked so it vibrates in a standing mode between two extreme positions a and b. Let upward motion correspond to positive velocities. When the string is in position c, the instantaneous velocity of points on the string:

1) is zero everywhere

2) is positive everywhere

3) is negative everywhere

4) depends on the position

along the string

When the string is flat, all points are moving through the equilibrium position and are therefore at their maximum velocity. However, the

direction depends on the locationdirection depends on the location of the point. Some points are moving upwards rapidly, and some points are moving downwards rapidly.

a

b

c

ConcepTest 11.19bConcepTest 11.19b Standing Waves IIStanding Waves IIA string is clamped at both ends and plucked so it vibrates in a standing mode between two extreme positions a and b. Let upward motion correspond to positive velocities. When the string is in position c, the instantaneous velocity of points on the string:

1) is zero everywhere

2) is positive everywhere

3) is negative everywhere

4) depends on the position

along the string

If you fill your lungs with

helium and then try

talking, you sound like

Donald Duck. What

conclusion can you

reach about the speed

of sound in helium?

1) speed of sound is less in helium

2) speed of sound is the same in helium

3) speed of sound is greater in helium

4) this effect has nothing to do with the speed in helium

ConcepTest 12.2cConcepTest 12.2c Speed of Sound III

If you fill your lungs with

helium and then try

talking, you sound like

Donald Duck. What

conclusion can you

reach about the speed

of sound in helium?

1) speed of sound is less in helium

2) speed of sound is the same in helium

3) speed of sound is greater in helium

4) this effect has nothing to do with the speed in helium

The higher pitch implies a higher frequency. In turn, since v = f, this means that the speed of the wave has increased (as long as the wavelength, determined by the length of the vocal chords, remains constant).

ConcepTest 12.2cConcepTest 12.2c Speed of Sound III

Follow-up:Follow-up: Why is the speed of sound greater in helium than in air? Why is the speed of sound greater in helium than in air?

You stand a certain distance away from a speaker and you hear a certain intensity of sound. If you double your distance from the speaker, what happens to the sound intensity at your new position?

1) drops to 1/2 its original value

2) drops to 1/4 its original value

3) drops to 1/8 its original value

4) drops to 1/16 its original value

5) does not change at all

ConcepTest 12.4aConcepTest 12.4a Sound Intensity I

You stand a certain distance away from a speaker and you hear a certain intensity of sound. If you double your distance from the speaker, what happens to the sound intensity at your new position?

1) drops to 1/2 its original value

2) drops to 1/4 its original value

3) drops to 1/8 its original value

4) drops to 1/16 its original value

5) does not change at all

For a source of a given power P, the intensity is given

by I = P/4r2. So if the distance doublesdistance doubles, the intensity

must decrease to one-quarterdecrease to one-quarter its original value.

ConcepTest 12.4aConcepTest 12.4a Sound Intensity I

Follow-up:Follow-up: What distance would reduce the intensity by a factor of 100? What distance would reduce the intensity by a factor of 100?

1) about the same

2) about 10 times

3) about 100 times

4) about 1000 times

5) about 10,000 times

A quiet radio has an intensity level

of about 40 dB. Busy street traffic

has a level of about 70 dB. How

much greater is the intensity of the

street traffic compared to the radio?

ConcepTest 12.5bConcepTest 12.5b Decibel Level II

increase by 10 dB increase intensity by factor of 101 (10)

increase by 20 dB increase intensity by factor of 102 (100)

increase by 30 dB increase by 30 dB increase intensity by factor of 10 increase intensity by factor of 1033 (1000) (1000)

1) about the same

2) about 10 times

3) about 100 times

4) about 1000 times

5) about 10,000 times

A quiet radio has an intensity level

of about 40 dB. Busy street traffic

has a level of about 70 dB. How

much greater is the intensity of the

street traffic compared to the radio?

ConcepTest 12.5bConcepTest 12.5b Decibel Level II

Follow-up:Follow-up: What decibel level gives an intensity a million times greater? What decibel level gives an intensity a million times greater?

(1) the long pipe

(2) the short pipe

(3) both have the same frequency

(4) depends on the speed of sound in the pipe

You have a long pipe

and a short pipe.

Which one has the

higher frequency?

ConcepTest 12.6aConcepTest 12.6a Pied Piper I

A shorter pipeshorter pipe means that the standing wave in

the pipe would have a shorter wavelengthshorter wavelength. Since

the wave speed remains the same, the frequency frequency

has to be higherhas to be higher in the short pipe.

(1) the long pipe

(2) the short pipe

(3) both have the same frequency

(4) depends on the speed of sound in the pipe

You have a long pipe

and a short pipe.

Which one has the

higher frequency?

ConcepTest 12.6aConcepTest 12.6a Pied Piper I

1) depends on the speed of sound in the pipe

2) you hear the same frequency

3) you hear a higher frequency

4) you hear a lower frequency

You blow into an open pipe

and produce a tone. What

happens to the frequency

of the tone if you close the

end of the pipe and blow

into it again?

ConcepTest 12.7ConcepTest 12.7 Open and Closed Pipes

In the open pipeopen pipe, ½ of a wave½ of a wave “fits”

into the pipe, while in the closed pipeclosed pipe,

only ¼ of a wave¼ of a wave fits. Because the

wavelength is larger in the closed wavelength is larger in the closed

pipepipe, the frequency will be lowerfrequency will be lower.

1) depends on the speed of sound in the pipe

2) you hear the same frequency

3) you hear a higher frequency

4) you hear a lower frequency

You blow into an open pipe

and produce a tone. What

happens to the frequency

of the tone if you close the

end of the pipe and blow

into it again?

ConcepTest 12.7ConcepTest 12.7 Open and Closed Pipes

Follow-up:Follow-up: What would you have to do What would you have to do to the pipe to increase the frequency?to the pipe to increase the frequency?

Observers A, B and C listen to a

moving source of sound. The

location of the wave fronts of the

moving source with respect to

the observers is shown below.

Which of the following is true?

1) frequency is highest at A

2) frequency is highest at B

3) frequency is highest at C

4) frequency is the same at all

three points

ConcepTest 12.11aConcepTest 12.11a Doppler Effect I

Observers A, B and C listen to a

moving source of sound. The

location of the wave fronts of the

moving source with respect to

the observers is shown below.

Which of the following is true?

1) frequency is highest at A

2) frequency is highest at B

3) frequency is highest at C

4) frequency is the same at all

three points

The number of wave fronts

hitting observer Cobserver C per unit time

is greatest -- thus the observed

frequency is highest there.

ConcepTest 12.11aConcepTest 12.11a Doppler Effect I

Follow-up:Follow-up: Where is the frequency lowest? Where is the frequency lowest?

You are heading towards an island in

a speedboat and you see your friend

standing on the shore, at the base of

a cliff. You sound the boat’s horn to

alert your friend of your arrival. If the

horn has a rest frequency of f0, what

frequency does your friend hear ?

1) lower than f0

2) equal to f0

3) higher than f0

ConcepTest 12.11bConcepTest 12.11b Doppler Effect II

You are heading towards an island in

a speedboat and you see your friend

standing on the shore, at the base of

a cliff. You sound the boat’s horn to

alert your friend of your arrival. If the

horn has a rest frequency of f0, what

frequency does your friend hear ?

1) lower than f0

2) equal to f0

3) higher than f0

Due to the approach of the sourceapproach of the source towards the stationary observer, the frequency is shifted higherfrequency is shifted higher. This is the same situation as depicted in the previous question.

ConcepTest 12.11bConcepTest 12.11b Doppler Effect II

In the previous question, the horn had a rest frequency of f0, and we found that your friend heard a higher frequency f1 due to the Doppler shift. The sound from the boat hits the cliff behind your friend and returns to you as an echo. What is the frequency of the echo that you hear?

1) lower than f0

2) equal to f0

3) higher than f0 but lower than f1

4) equal to f1

5) higher than f1

ConcepTest 12.11cConcepTest 12.11c Doppler Effect III

In the previous question, the horn had a rest frequency of f0, and we found that your friend heard a higher frequency f1 due to the Doppler shift. The sound from the boat hits the cliff behind your friend and returns to you as an echo. What is the frequency of the echo that you hear?

1) lower than f0

2) equal to f0

3) higher than f0 but lower than f1

4) equal to f1

5) higher than f1

The sound wave bouncing off the cliff has the same frequency f1 as

the one hitting the cliff (what your friend hears). For the echo, you you

are now a moving observer approaching the sound waveare now a moving observer approaching the sound wave of

frequency f1 so you will hear an even higher frequencyeven higher frequency.

ConcepTest 12.11cConcepTest 12.11c Doppler Effect III