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BaLLatris [955]
3 years ago
7

a whistle you use to call your hunting dog has a frequency of 21 khz, but your dog is ignoring it. you suspect the whistle may n

ot be working, but you can't hear sounds above 20 khz. to test it, you ask a friend to blow the whistle, then you hop on your bicycle.At what minimum speed should you ride to know if the whistle is working?
Physics
1 answer:
laila [671]3 years ago
4 0

To solve this problem we will apply the concepts related to the Doppler effect. According to this concept, it is understood as the increase or decrease of the frequency of a sound wave when the source that produces it and the person who captures it move away from each other or approach each other. Mathematically this can be described as

f = f_0 (\frac{v-v_0}{v})

Here,

f_0 = Original frequency

v_0 = Velocity of the observer

v = Velocity of the speed

Our values are,

v = 340m/s \rightarrow \text{Speed of sound}

f = 20kHz \rightarrow \text{Apparent frequency}

f_0 = 21kHz \rightarrow \text{Original frequency}

Using the previous equation,

f = f_0 (\frac{v-v_0}{v})

Rearrange to find the velocity of the observer

v_0 =v (1-\frac{f}{f_0})

Replacing we have that

v_0= (340m/s)(1-\frac{20kHz}{21kHz})

v_0 = 16.19m/s

Therefore the velocity of the observer is 16.2m/s

You might be interested in
A city planner needs to make a model of the city. In real life, the tallest tree in the city is 40 feet tall. The shortest tree
Verdich [7]
To solve this you must set up what is called a proportion.  A proportion is a way of comparing two comparing values where one of the four values is missing.  In your problem the missing value is the height of the smallest tree in the model.

To set up a proportion, you need all of your values.  The easiest way to do this is to list them:

Highest tree in real life:  40ft
Highest tree in model:  10ft
Smallest tree in real life:  4ft
Smallest tree in model:  x

So know you can set your proportion like this:

40/4 = 4/x

(When setting up a proportion, you always want to have the values belong to each other.  For example don't put the height of the small tree in the model underneath the value of the highest tree in real life.)

So know to find what the x values equals, we need to cross multiply.  And then all that's left after that is to solve for x.

40 times x = 4 times 4

40x = 16

x = 2.5

The smallest tree in the model should equal 2.5 feet.

Hope this helps! :)



6 0
3 years ago
Tudy the images about geologic time.
Fittoniya [83]

Answer:

The first flowering plants appeared in the Mesozoic era, not the Paleozoic era

Explanation:

The Mesozoic era is well known and most famous because of the rule of the dinosaurs which were the dominant animals for most of this are. Also, it is the era in which the mammals appeared, though they lived in the shadows of the dinosaurs and only became dominant after their extinction. Another important evolution that took place and is not mentioned very often is the appearance of the first flowering plants. This was a revolutionary trait for the plants, and it helped them to survive in the changing climate on Earth. Soon this trait enabled this type of plants to spread out significantly and to become one of the most dominant organisms on the planet in the following era.

6 0
3 years ago
SCIENCE HELP! PLEASE HELP URGENT!
Nonamiya [84]
It is also tripled, there is a rule to everything, whatever you do to one thing, you do the exact thing to the other. Hope this solves it :)
6 0
2 years ago
Quick puzzle question. If god created the universe who created god?
mrs_skeptik [129]

Answer:

My mom always told me he was just there

Explanation:

4 0
3 years ago
Read 2 more answers
A 3 mm inside diameter tube is placed in a fluid with a surface tension of 600 mN/m and density of 3.7 g/cm3. The contact angle
Aleks04 [339]

Answer: The height of the fluid rise is 0.01m

Explanation:

Using the equation

h = (2TcosѲ )/rpg

h= height of the fluid rise

diameter of the tube =3mm

radius of the tube= 3/2 =1.5mm=0.0015

T= surface tension = 600mN/m=0.6N/m

Ѳ = contact angle = 60^oC

p= density =3.7g/cm3= 3700kg/m3

g= acceleration due to gravity =9.8m/s2

h = ( 2*0.6*0.5)/(0.0015*3700*9.8)

h = 0.6/54.39

h= 0.01m

Therefore,the height of the fluid rise is 0.01m

8 0
3 years ago
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