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3 years ago

The velocity of the wave involved in the Doppler effect:

Physics

2 answers:

pentagon [3]3 years ago

5 0

Answer:

b. depends upon the medium in which it occurs

Explanation:

When source of sound and observer moves relative to each other then in that case the relative motion between them will change the frequency that is observed by the observer.

It is known as Doppler's effect. In that case the velocity of wave depends on the medium in which wave travels.

As we know that wave speed is given as

$v = \sqrt{\frac{\gamma RT}{M}}$

so here as the medium of the wave changes the speed of wave also be different so here correct answer will be

b. depends upon the medium in which it occurs

Margarita [4]3 years ago

4 0

The Doppler Effect provides the equation for the calculation of apparent frequency:

f=fo[vo/(vo-vr)]

where:
vo=source wave velocity
vr=relative speed between source and observer
f=apparent frequency
fo=source frequency

The velocity of the doppler wave is
v=λf

where λ is light wavelength. Hence,

v=λfo[vo/(vo-vr)]

Based on the equation, we can say that wave velocity will always be defined by one and only one wavelength.

Therefore the answer is letter C.

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A physics teacher performing an outdoor demonstration suddenly falls from rest off a high cliff and simultaneously shouts "Help"

Digiron [165]

Answer: a) The cliff is 532.05m high

b) Her speed just before hitting the ground is 102.12 m/s

Explanation: To solve This, I'll use a sketch diagram, attached to this solution,

In 3seconds, the teacher heard the echo of her initial scream back. We can obtain the distance the teacher had fallen at the end of 3 seconds using the equations of motion,

Y1 = ut + 0.5g(t^2)

Since she's falling under the influence of gravity, her initial velocity, u = 0m/s, g = 9.8m/s2, t = 3s

Y1, distance she fell through in 3 seconds = 0.5×9.8(3^2) = 44.1m

Let the total height of the cliff be (44.1 + x); where is the remaining height of cliff that the teacher will fall through.

Using the equations of motion again, we can obtain distance travelled by the sound waves in 3s. sound waves travel with a constant speed of 340m/s, no acceleration,

Y2 = ut + 0.5g(t^2) where g = 0, u = 340m/s, t = 3seconds

Y2 = 340 × 3 = 1020m

But in 3 secs, the sound waves would have travelled through the total height of the cliff (44.1 + x) and back to the teacher's current height, x. That is, 1020 = 44.1 + x + x

x = 487.95m

So, total height of cliff = 44.1 + 487.95 = 532.05m

b) the speed of the teacher just before she hits the ground.

Using the equations of motion again,

(V^2) = (U^2) + 2gs

Where v is the final velocity to be calculated

U is the initial velocity = 0m/s

g is acceleration due to gravity = 9.8m/s2

S is the total height she fell through, that is, the height of the cliff = 532.05m

(V^2) = 0 + 2×9.8×532.05 = 10428.18

V = √(10428.18) = 102.12m/s

QED!

4 0

3 years ago

Pe=___

Nesterboy [21]

Answer:

H = start height (v = 0)

h = present height

v = present speed

assuming no friction

total energy = PE + KE

mgH = mgh + .5mv^2

if PE = KE then

mgH = mgh + mgh

h = H/2

potential energy = kinetic energy when object is at half its start height.

Explanation:

8 0

3 years ago

28. Which of the following correctly shows the order of highest amount of friction to the lowest amount of

Bad White [126]

Answer:

$\mathrm{d.\:Static,\: Sliding,\:Rolling}$

Explanation:

Static friction occurs when an object initially starts at rest. When the surfaces of the materials touch, the microscopic unevenness interlock greatest with each other, causing the most friction out of the three.

During sliding friction, an object is already moving or in motion. The microscopic surfaces still interlock, but because the object is in motion, it has a momentum. Therefore, the magnitude of sliding friction is less than that of static friction.

Rolling friction occurs when an object rolls across some surface. Rather than surfaces interlocking, rolling friction is caused by the constant distortion of surfaces. As it rolls, the surfaces of the object are constantly wrapping and changing. This distortion causes the rolling friction. However, it is much less in magnitude when compared to static or sliding friction.

4 0

3 years ago

PLEASE ANSWER ASAP!.!.!!.!!!!.!.!.

lbvjy [14]

1. Most PE, because PE is directly proportional to distance (height)
Height: 100 meters
Speed: 0 mph

2. Most KE, because KE is directly proportional to speed
Height: 10 meters
Speed: 40 mph

3. Most TE, average KE
Height: 10 meters
Speed: 40 mph

4. The skater gains thermal energy as she goes down the slope, because the speed of the skater increases, so it increases the total kinetic energy of the particles, and makes them vibrate faster, resulting in a higher temperature.

8 0

3 years ago

In the flow past a compression corner, the upstream Mach number and pressure are 3.5 and 1 atm, respectively. Downstream of the

yulyashka [42]

Answer:

$\theta=23.7^{\circ}$