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ozzi
3 years ago
6

You are walking along a small country road one foggy morning and come to an intersection. While you are crossing, you hear an am

bulance siren. As a paramedic, you know that the siren sounds at a frequency of 7.87 kHz. But, as an amateur musician with perfect pitch, you can tell that the frequency you are hearing is actually 8.61 kHz. Is the ambulance moving toward or away from you? The ambulance is moving toward you! At what speed is the ambulance traveling?_____ mph?
Physics
1 answer:
emmainna [20.7K]3 years ago
7 0

Answer:

64.945 miles per hour

Explanation:

Since the frequency of sound heard is higher than actual frequency, the ambulance is moving towards you!

The frequency of sound waves as heard from a distance for a sound wave coming towards one at v₀ m/s and whose real frequency is f₀ is given by

+f = f₀/[1 - (v₀/v)]

+f = frequency of sound as heard from the distance away = 8.61 KHz

f₀ = real frequency of sound = 7.87 KHz

v₀ = velocity at which the sound source is moving towards the reference point = ?

v = velocity of sound waves = 343 m/s

8.61 = 7.87/(1 - (v₀/v))

1 - (v₀/343) = 0.9141

v₀/343 = 1 - 0.9141 = 0.0859

v₀ = 343 × 0.0859 = 29.48 m/s = 64.945 miles per hour

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Narysuj wykres zależności v(t) jeśli w chwili początkowej t=0 V=10m/s w każdej sekundzie szybkość zmniejsza się o 1m/s . Po jaki
irina1246 [14]

1) See graph in attachment

2) 10 s

3) 50 m

Explanation:

1)

In this problem, we have an object initially moving with a velocity of

v = 10 m/s

when the time is

t = 0 s

Then, we are told that the speed of the object is decreasing by 1 m/s every  second. This means that on a velocity-time graph, the motion will be represented by a straight line, starting from v = 10 when t = 0, and decreasing by 1 m/s every second.

The result can be found in the graph in attachment.

Moreover, we can also infer that the motion of the object is accelerated (because velocity is changing), and that the acceleration is constant and it is equal to

a=1 m/s^2

which is equivalent to the gradient of the line in the velocity-time graph.

2)

In this part, we want to find after what time the body will stop its motion.

To do that, we can use the following suvat equation:

v=u+at

where

v is the final velocity

u is the initial velocity

a is the acceleration

t is the time

In this problem:

u = 10 m/s is the initial velocity of the body

a=-1 m/s^2 is the acceleration

v = 0 m/s, because we want to find the time T at which the body will stop

Re-arranging the equation, we find:

T=-\frac{u}{a}=-\frac{10}{-1}=10 s

3)

In order to find the total distance covered by the body during its accelerated motion, we have to use another suvat equation:

s=ut+\frac{1}{2}at^2

where

s is the distance covered

u is the initial velocity

t is the time

a is the acceleration

In this problem:

u = 10 m/s is the initial velocity

a=-1 m/s^2 is the acceleration

t = 10 s is the time it takes for the body to stop (found in part 2)

Solving for s, we find the distance covered:

s=(10)(10)+\frac{1}{2}(-1)(10)^2=50 m

7 0
4 years ago
A uniform rod of length L, mass M, is suspended by two thin strings. Which of the following statements is true
Fantom [35]

Answer:

(d) not enough info

Explanation:

because it doesn't specify where the strings are attached

if it was the two ends of the rod then T1 would be equal to T2

6 0
3 years ago
What is the period of a wave with a frequency of 100 Hz and a wavelength of 2.0 m
spin [16.1K]

The answer for the following answer is answered below.

  • <u><em>Therefore the time period of the wave is 0.01 seconds.</em></u>
  • <u><em>Therefore the option for the answer is "B".</em></u>

Explanation:

Frequency (f):

The number of  waves that pass a fixed place in a given amount of time.

The SI unit of frequency is Hertz (Hz)

Time period (T):

The time taken for one complete cycle of vibration to pass a given point.

The SI unit of time period is seconds (s)

Given:

frequency (f) = 100 Hz

wavelength (λ) = 2.0 m

To calculate:

Time period (T)

We know;

According to the formula;

<u>f =</u>\frac{1}{T}<u></u>

Where,

f represents the frequency

T represents the time period

from the formula;

  T = \frac{1}{f}

 T = \frac{1}{100}

  T = 0.01 seconds

<u><em>Therefore the time period of the wave is 0.01 seconds.</em></u>

5 0
3 years ago
Read 2 more answers
Sound waves strike a glass and cause it to shatter.
e-lub [12.9K]
1. Resonance. Mechanical waves act on or through a medium, these waves can often have frequencies that are synchronized in a way that makes them act on the matter in the medium more "aggressively."
3 0
3 years ago
In a circus performance, a monkey on a sled is given an initial speed of 4.3 m/s up a 24◦ incline. The combined mass of the monk
Serggg [28]

Answer:

d = 1.15 m

Explanation:

  • In absence of friction, the change in kinetic energy of the combined mass of the monkey and the sled, must be equal (with opposite sign), to the change in gravitational potential energy:

        ΔK = -ΔU

  • When friction is not negligible, the change in mechanical energy, must be equal to the work done by non-conservative forces (kinetic friction in this case):

       ΔK + ΔU = Wnc (1)

  • As the monkey + sled reach to the maximum distance up the incline, they will come momentarily to a stop, so the final kinetic energy is 0.

        (K_{f} -K_{o}) = 0 - \frac{1}{2} * m*v_{o} ^{2} = -\frac{1}{2} *22.5kg*(4.3m/s)^{2} = -208.1J

  • The change in gravitational energy, can be written as follows:

        (U_{f} - U_{o} ) = m*g*h - 0 = m*g*h = \\ \\ 22.5 kg*9.8 m/s2*d*sin (24 deg) = 89.7J*d

  • The sum of these two quantities, must be equal to the work done by the friction force, along the distance d up the incline:

        W_{nc} = -\mu k*N*d

  • The normal force, always normal to the surface, must be equal and opposite to the component of the weight normal to the incline:

        N = m*g*cos \theta = m*g*cos (24 deg) = \\ \\ 22.5 kg*9.8m/s2*0.913 = 201.4 N

  • Replacing in the equation for Wnc:

        W_{nc} = -\mu k*N*d = -0.45*201.4 N*d = -90.6 N*d

  • We can return to the equation (1) and solve for d:

        -208.1 J + 89.7N*d = -90.6N*d\\\\  d = \frac{208.1}{180.3} =1.15 m

3 0
3 years ago
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