Question

@agent0smith

Answer 1

When needed, use 340 m/s for the speed of sound and 3.00 x 108 m/s for the speed of light.

A hiker determines the length of a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake. She hears the echo 2.20 s after shouting. How long is the lake?
374 m


170 m


748 m


270 m

Answer 2

Show me how to solve it

Answer 3

Distance = speed*time

speed =340
time = half of the 2.2 seconds, since the sound goes across the lake and back

Answer 4

374m

Answer 5

For 1.1*340 that looks about right

Answer 6

Calculate the difference in the wavelengths in air for sounds in the maximum range of human hearing, 20 Hz to 20,000 Hz.
17 m
0.270 m
48 m
1.70 m

Answer 7

speed = frequency*wavelength

Answer 8

Speed =340, freq = 20

then do it again for
Speed =340, freq = 20,000

Answer 9

Would I add those together?

Answer 10

difference = subtract

Answer 11

Ooh yea my bad okk

Answer 12

17m?

Answer 13

Idk. I'm eaiting :P

speed = frequency*wavelength
where speed =340, freq = 20

then
speed = frequency*wavelength
where speed =340, freq = 20,000

then subtract the two

Answer 14

I did 340/20=17
340/20000=.017
17-.017=16.9
Rounded would be 17m

Answer 15

What is the wavelength of a 34 MHz ultrasonic sound wave?

10. m
8.8 m
0.270 m
0.00001 m

Answer 16

speed = frequency*wavelength
where speed =340, freq = 34,000,000

Answer 17

I'm getting an error in my calc

Answer 18

I'm getting 1E-5

Answer 19

I'm supposed to be dividing 340/34000000 right?

Answer 20

E means "times 10 to the power of"

Answer 21

ok so .00001m

Answer 22

If you listento radio, you know stations have numbers like 92.3. The number refers to the frequency of the channel in megahertz, as in 92.3 MHz. What is the wavelength of the radio wave?

Question 30 options:

3,300,000 m


0.0000037 m


3.7 m


3.3 m

Answer 23

Would I use the same formula?

Answer 24

speed = frequency*wavelength

speed is 3*10^8, freq=92.3*10^6

Answer 25

ok can you explain why would I square those or whtvr?

Answer 26

What? don't square them

Answer 27

Well ok why can't I just do 92.3 but 92.3*10^6??

Answer 28

Mhz - the M means million or 10^6

Answer 29

ok. I got it... 3.3m
The frequency of the A note on a piano is 220 Hz. What is the frequency of the high A note, one octave above that?

Question 31 options:

221 Hz


230 sec


320 Hz


440 Hz

Answer 30

If only I could remember the fckn formula an question wording

Answer 31

You'd have to google octaves

Answer 32

Nvm I got it. It's 440

Answer 33

So the full length is 30 right?

Answer 34

Yeah, wavelength looks about 7cm

Answer 35

so
Question 32 options:

20.0 cm

1.0 cm

6.7 cm

4.55 cm

Answer 36

See last post :P

Answer 37

closest is 6.7

Answer 38

What is the amplitude?
5 cm
10 cm
6.7 cm
20 cm

Answer 39

Distance from middle to top is about 5 units which is 5cm

Answer 40

A wave on a rope has 6 nodes, including one at each end. If the wave train or system of waves is 5 meters long, what is the wavelength?

6 m
1.2 m
5 m
2 m

Answer 41

6m?

Answer 42

There is 3 nodes in one wavelength. There would be 2.5 wavelengths in the 5m long string. I drew it to work it out.

So 5m/2.5

Answer 43

A sound wave has a length of 0.66 meters. If the frequency of the wave is 512 Hz (high C), what is the wave velocity?

Question 35 options:

511 m/sec


0.00129 m/s


776 m/s


338 m/s

Answer 44

same formula as every other question :P

Answer 45

.66(512)??

Answer 46

338m/s?

Answer 47

Yep

Answer 48

A standing wave on a string has a velocity of 42 m/s and a period of 0.01 s. What is the frequency of the wave?

Question 36 options:

100 Hz


260 Hz


0.42 Hz


10 sec

Answer 49

i did 42/.01 and got 4200

Answer 50

All you need is: Freq = 1/period

period is 0.01