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alex41 [277]
3 years ago
14

A truck moving at 45 m/s passes a police car moving at 36 m/s in the opposite direction. if the frequency of the siren is 500 Hz

relative to the police car, what is the frequency heard by an observer in the truck after the police car passes the truck
Physics
1 answer:
elena-14-01-66 [18.8K]3 years ago
7 0

Answer: observed frequency (f') = 511.97Hz

Explanation: when there is a relative motion between an observer and a sound source, the frequency of sound wave perceived by the observer is different from the frequency of originally sent out by the sound source.

This is called Doppler effect and given mathematically below as

f' = (v + v') /(v- vs) * f

f' = observed frequency

v = speed of sound in air = 340m/s

v' = velocity of observer= 45m/s

vs = velocity of source relative to observer = - 36m/s ( the negative sign came as a result of the fact that the velocity of the source is in opposite direction to the velocity of the observer)

f = original frequency of sound source = 500Hz

f' = (340 + 45)/{340 -(-36)} * 500

f' = 385/ (340 + 36) * 500

f' = 385/ 376 * 500

f' = 1.0239 * 500

f' = 511.97Hz

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Calculate the energy gained by an ice block in the following experiment.
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The heat is exchanged when two different temperature objects come in contact. The energy gained by an ice block is 2.3 Joules.

<h3>What is temperature?</h3>

Temperature is the degree of hotness and coldness of the object.

A 7g block of ice was added to a coffee cup full of 103.4 grams of water. The water had an initial temperature T₁ = 24.5 C and a final temperature T₂ = 19.2 C after all the ice had melted.

Heat lost by water = Heat gained by ice

Qgain = ms(T₂ -T₁ )

Substituting the value for mass of water m =103.4 g= 0.1034 kg , specific heat of water s = 4.18 kJ/kg and temperature values, we get

Qgain = 0.1034 x 4.18 x (24.5 - 19.2)

Qgain = 2.3 Joules

Thus, the energy gained by an ice block is 2.3 Joules.

Learn more about temperature.

brainly.com/question/20459283

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7 0
1 year ago
If two charged objects in a laboratory are brought to a distance of 0.22 meters away from each other. What is
zysi [14]

Answer:

q_2=2.47\times 10^{-4}\ C

Explanation:

The charge on one object, q_1=9.9\times 10^{-5}\ C

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Let q₂ is the charge on the other sphere. The electrostatic force between two charges is given by the formula as follows :

F=\dfrac{kq_1q_2}{r^2}\\\\q_2=\dfrac{Fr^2}{kq_1}\\\\q_2=\dfrac{4550\times (0.22) ^2}{9\times 10^9\times 9.9\times 10^{-5}}\\\\q_2=2.47\times 10^{-4}\ C

So, the charge on the other sphere is 2.47\times 10^{-4}\ C.

7 0
3 years ago
A brick is resting on a smooth wooden board that is at a 30° angle. What is one way to overcome the static friction that is hold
lubasha [3.4K]

Answer:

to overcome the out of friction we must increase the angle of the plane

Explanation:

To answer this exercise, let's propose the solution of the problem, write Newton's second law. We define a coordinate system where the x axis is parallel to the plane and the other axis is perpendicular to the plane.

X axis

       fr - Wₓ = m    a                      (1)

Y axis  

       N- W_{y} = 0

       N = W_{y}

let's use trigonometry to find the components of the weight

        sin θ = Wₓ / W

        cos θ = W_{y} / W

        Wₓ = W sin θ

        W_{y} = W cos θ

the friction force has the formula

         fr = μ N

         fr = μ Wy

         fr = μ mg cos θ

from equation 1

at the point where the force equals the maximum friction force

in this case the block is still still so a = 0

           F = fr

           F = (μ  mg) cos θ

We can see that the quantities in parentheses with constants, so as the angle increases, the applied force must be less.

This is the force that balances the friction force, any force slightly greater than F initiates the movement.

Consequently, to overcome the out of friction we must increase the angle of the plane

the correct answer is to increase the angle of the plane

4 0
3 years ago
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RUDIKE [14]

Answer:

0.01 m

Explanation:

Since the speed of light is 3.0×10^8 m/s

Use the equation,

Wavelength = speed ÷ frequency

Wavelength = 3.0×10^8 ÷ 3×10^10

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