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faltersainse [42]
3 years ago
14

A police car with its 300-Hz siren is moving toward a warehouse at 30 m/s, intending to crash through the door. The sound bounce

s off the warehouse door and travels back to the police officer in the moving car. Using 340 m/s as the speed of sound, what is the beat frequency the officer hears
Physics
1 answer:
Lady bird [3.3K]3 years ago
8 0

Answer: The frequency heard will be f = 275.675Hz

Explanation: When an object emitting sound is moving, it occurs a phenomenon called Doppler shift or Doppler effect. What happens is that the sound gets higher when the moving object comes closer the observer and becomes lower after it passes, This change is due to the quantity of waves that passes through an area in an unit of time.

The formula to calculate the Doppler effect is as follows

f = (\frac{c}{c+Vs}) · f₀

f is the observed frequency;

c is the speed of sound;

Vs is velocity of the source;

f₀ is the emitted frequency of source;

Substituting and calculating,

f = \frac{340}{340+30} · 300

f = 275.675 Hz

Thus, the frequency heard by the police officer is 275.675Hz.

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<h2>Answer:</h2>

Low melting points and electrical conductivity in solids are not common properties of ionic solids.

<h3>Explanation:</h3>

In ionic compounds the electrons involved in the bonding are tightly packed under the influence of electrostatic force of attraction. So the movement of these electrons is very difficult.

In the melting point the bond breaking between the atoms is involved. Hence in case of ionic compound there is a high amount of energy needed to break the ionic bonds.

Electrical conductivity involves the free movement of electrons which is impossible in ionic solids.

So low melting points and electrical conductivity in solids are not common properties of ionic solids.

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3 years ago
Question 8
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Answer:

3.6 s

Explanation:

100 km/hr =27.77 m/s

100/27.77=3.6 sec

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2 years ago
What type of reaction is shown in the following chemical equation: 2H2O → 2H2 + O2?
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Answer:

Decomposition

Explanation:

A reaction in which one compound breaks up into two or more compounds is called a decomposition reaction.

4 0
3 years ago
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When more than one wave is in the same location at the same time, then there is _____ between the waves?
igor_vitrenko [27]
The sentence can be completed as follows:
"<span>When more than one wave is in the same location at the same time, then there is interference between the waves"

In fact, when there are two or more waves in the same location at the same time, their amplitude sum together. The two extreme possibilities are:
- costructive interference: the two waves arrive on phase at the same location (=their crests arrive at the same location at the same time). In this case, the amplitudes of the waves sum together and the resultant wave has greater amplitude.
- destructive interference: the two waves arrive out of phase at the same location. In this case, the amplitudes of the two waves cancel out, and the resultant wave has amplitude zero.</span>
4 0
3 years ago
A uniform cylinder of radius 25 cm and mass 27 kg is mounted so as to rotate freely about a horizontal axis that is parallel to
Alisiya [41]

Answer:

Explanation:

                                                     STEP 1

<u>Given</u>

Radius of cylinder = r = 25cm, 2.5m

mass = 27kg

cylinder is mounted so as to rotate freely about a horizontal axis that is parallel to and 60cm to the central logitudinal axis of the cylinder

height = 0.6m

<u>part 1</u>

The cylinder is mounted so as to rotate freely about a horizontal axis tha is paralle to 60cm from the central longitudinal axis of then cylinder. The rotational inertia of the cylinder about the axis of rotation is given by

<em>I = Icm + mh²</em>

<em>∴ I = 1/2mr² + mh² = 1/2x27x (0.5)² + 20  x  (0.6)²</em>

<em>I=13.09kg.m²</em>

where

<em>I</em>cm is the rotational inertia of the cylinder about its central axis

m is the mass of the cylinder

h is the distance between the axis of the rotation and the central axis of the cylinder

r is the radius of the cylinder

<em>                                        </em><em> I=13.09kg.m²</em>

<em>part2</em>

<em>from the conservation of the total mechanical energy of the meter stick, the change in gravitational potential energyof the meter stick plus the change in kinetic energy must be zero</em>

<em>Δk + Δu = 0</em>

<em>1/2 </em>I(w²-w²) = Ui-Uf

1/2 x 13.09w² = mgh

∴w=√20 x 9.8 x 0.6/(1/2 x 13.09) =117.6/6.5

w=18.09rad/s

5 0
3 years ago
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