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jasenka [17]
4 years ago
13

If a sound with frequency fs is produced by a source traveling along a line with speed vs. If an observer is traveling with spee

d vo along the same line from the opposite direction toward the source, then the frequency of the sound heard by the observer is fo = c + vo c − vs fs where c is the speed of sound, about 332 m/s. (This is the Doppler effect.) Suppose that, at a particular moment, you are in a train traveling at 45 m/s and accelerating at 1.1 m/s2. A train is approaching you from the opposite direction on the other track at 46 m/s, accelerating at 1.6 m/s2, and sounds its whistle, which has a frequency of 459 Hz. At that instant, what is the perceived frequency that you hear? (Round your answer to one decimal place.) Hz How fast is it changing? (Round your answer to two decimal places.) Hz/s
Physics
1 answer:
Alexus [3.1K]4 years ago
7 0

Answer:

457.81 Hz

Explanation:

From the question, it is stated that it is a question under Doppler effect.

As a result, we use this form

fo = (c + vo) / (c - vs) × fs

fo = observed frequency by observer =?

c = speed of sound = 332 m/s

vo = velocity of observer relative to source = 45 m/s

vs = velocity of source relative to observer = - 46 m/s ( it is taking a negative sign because the velocity of the source is in opposite direction to the observer).

fs = frequency of sound wave by source = 459 Hz

By substituting the the values to the equation, we have

fo = (332 + 45) / (332 - (-46)) × 459

fo = (377/ 332 + 46) × 459

fo = (377/ 378) × 459

fo = 0.9974 × 459

fo = 457.81 Hz

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A 400 hp engine in a 1,600 kg car applies maximum force for 2 seconds to accelerate the car onto the
babymother [125]

Answer:

I will assume that “maximum force” implies the constant application of power  P  = 400 hp (international) to accelerating the vehicle. The force will therefore vary with speed as the vehicle accelerates. I will also assume that all engine energy goes into accelerating the vehicle, rather than rotating elements like its wheels.

In this case the 400 hp (equivalent to 298,280 watts) is applied for time  t  = 2 seconds. Therefore the kinetic energy of the vehicle is increased by:

ΔKE=Pt=(298,280)(2)=596,560  joules.

The initial kinetic energy is:

KEinitial=12mv2

=(0.5)(1600)(82)=51,200  joules.

Therefore final kinetic energy is:

KEfinal=KEinitial+ΔKE

=51,200+596,560

=647,760  joules

Therefore final vehicle velocity can be found:

KEfinal=12mv2

v=2KEfinalm−−−−−−−−√

=(2)(647,760)1600−−−−−−−−−−−√

= 28.455 m/s

Explanation:

4 0
3 years ago
If constants aren't given in an experiment, what can be constant in the experiment?
mario62 [17]

Answer:

Anything in an experiment that remains unchanged.

Explanation:

An example could be the temperature of the laboratory room. If there is something that has an effect on an experiment that is not variable, it is a constant. Another constant could be, say, if you were doing calculations with the same amount and kind of fluid throughout the experiment, then that fluid would also be a constant.

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3 years ago
Which of the following causes tornados A. Dry climates B.Sationary fronts B. Condensation D. Wind shear
natta225 [31]
The answer is wind shear (D)
8 0
4 years ago
A ship can carry more load than aeroplane of same size. why?​
stepladder [879]

Answer:

density of water is much greater than density of air

Explanation:

when body is in fluid it carries weight which is always equal to upthrust

upthrust is given as

upthrust= density of fluid ×strength of gravitational field g × volume of body in fluid

as volume of ship and aeroplane is same and strength of gravitational field or acceleration due to gravity is same hence upthrust depens upon density of fluid .

density of air is about 1.2 kg/m^3  and density of water is 1000kg/m^3 hence ship carries more load

8 0
4 years ago
A sanding disk with rotational inertia 6.5 x 10-3 kg·m2 is attached to an electric drill whose motor delivers a torque of magnit
xeze [42]

Answer:

The angular momentum and angular velocity are 1.134 kg.m²/s and 174.5 rad/s.

Explanation:

Given that,

Moment of inertia I= 6.5\times10^{-3}\ kg.m^2

Torque = 21 N.m

Time dt = 54 ms

(a). We need to calculate the angular momentum

Using formula of torque

\tau=\dfrac{dL}{dt}

dL =\tau\times t

Where, dL = angular momentum

t = time

\tau = torque

Put the value into the formula

dL=21\times0.054

dL=1.134\ kg.m^2/s

(b). We need to calculate the angular velocity of the disk

Using formula of angular velocity

dL=I\omega

\omega=\dfrac{dL}{I}

\omega=\dfrac{1.134}{6.5\times10^{-3}}

\omega=174.5\ rad/s

Hence, The angular momentum and angular velocity are 1.134 kg.m²/s and 174.5 rad/s.

3 0
3 years ago
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