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tia_tia [17]
3 years ago
12

The siren of a police car at rest emits at a predominant frequency of 1980 Hz. What frequency will you hear if you are at rest a

nd the police car moves at 34.3.0m/s (a) toward you, and (b) away from you? Please Explain
Physics
1 answer:
Naddika [18.5K]3 years ago
6 0

Answer:

(a) 1782 Hz (b) 2178 Hz

Explanation:

The predominant frequency =1980 Hz

The speed of the police car =34.3 m/sec

The speed of sound in air =343 m/sec

(a) When the car moves towards you

According to Doppler's effect

f=f_0\frac{v-v_s}{v}=1980\times \frac{343-34.3}{343}=1782Hz

(b) When the car moves away from you

f=f_0\frac{v+v_s}{v}=1980\times \frac{343+34.3}{343}=2178Hz

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The acceleration of the car is 0.8049m/s^{2}.It takes 13.802s to travel the 230 m.

<h3>What is acceleration?</h3>

In mechanics, acceleration refers to the rate at which an object's velocity with respect to time varies. Acceleration is a vector quantity (in that they have magnitude and direction). The direction of an object's acceleration is determined by the direction of the net force acting on it. Newton's Second Law states that the combined effect of two factors determines how much an item accelerates: 

(i) It follows that  the magnitude of the net balance of all external forces acting on the object is directly proportional to the magnitude of this net resulting force, and

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Calculations:

40 km/hr ----- 11.11m/s

80 km/hr ----- 22.22m/s

v^{2} -u^{2} =2as\\22.22^{2} - 11.11^{2} = 2 x a x 230\\ 370.296=460a\\ a= 0.8049m/s^{2} \\

Time taken

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The correct answer is :

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We can obtain the horizontal component by applying the trigonometric identity of Cos(Ф), and if we obtain the component on the x axle, such as 22000 (m)×Cos(51°) = x, we may determine that x = 13845.05 metres. We need to obtain the vector components because we already know the distance and the angle.

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The car’s velocity as a function of time is b + 2ct and the car’s average velocity during this interval is 0.9 m/s.

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The average velocity of the car is calculated as follows;

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Thus, the car’s velocity as a function of time is b + 2ct and the car’s average velocity during this interval is 0.9 m/s.

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