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Reil [10]
2 years ago
10

A police car is driving north with a siren making a frequency of 1038 hz. Moops is driving north behind the police car at 12 m/s

and hard a frequency of 959hz. How fast is the police car going?
Physics
1 answer:
Marianna [84]2 years ago
8 0

Answer:

The police car is moving at 41.24 m/s.

Explanation:

To find the speed of the police car we need to use the Doppler equation:

f = f_{0}(\frac{v + v_{r}}{v + v_{s}})      

Where:

v: is the speed of the sound = 343 m/s

v_{r}: is the speed of the receiver = 12 m/s

v_{s}: is the speed of the source =?

f: is the observed frequency = 959 Hz

f₀: is the emitted frequency = 1038 Hz          

Both terms are positive in the fraction because the velocity of the sound is in the opposite direction to both velocities of the police car and the other car.  

By solving the above equation for v_{s} we have:        

v_{s} = \frac{f_{0}(v + v_{r})}{f} - v = \frac{1038(343 + 12)}{959} - 343 = 41.24 m/s  

Therefore, the police car is moving at 41.24 m/s.

I hope it helps you!                  

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4 0
2 years ago
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A balloon is filled to a volume of 7.00*10^2 mL at a temperature of 20.0°C. The balloon is then cooled at constant pressure to a
wolverine [178]

The final volume of the gas is 238.9 mL

Explanation:

We can solve this problem by using Charle's law, which states that for a gas kept at constant pressure, the volume of the gas (V) is proportional to its absolute temperature (T):

\frac{V}{T}=const.

Which can be also re-written as

\frac{V_1}{T_1}=\frac{V_2}{T_2}

where

V_1, V_2 are the initial and final volumes of the gas

T_1, T_2 are the initial and final temperature of the gas

For the gas in the balloon in this problem, we have:

V_1 = 7.00\cdot 10^2 mL = 700 mL is the initial volume

T_1=20.0^{\circ}C+273=293 K is the initial absolute temperature

V_2 is the final volume

T_2 = 1.00\cdot 10^2 K = 100 K is the final temperature

Solving for V_2,

V_2 = \frac{V_1 T_2}{T_1}=\frac{(700)(100)}{293}=238.9 mL

Learn more about ideal gases:

brainly.com/question/9321544

brainly.com/question/7316997

brainly.com/question/3658563

#LearnwithBrainly

6 0
3 years ago
Calculate the kinetic energy of a 750 kg compact car moving 50 m/s.
k0ka [10]
935,500 joules because when we use the KE formula KE=1/2mv^2;
KE=1/2(750)(50)^2
KE=375(2500)
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6 0
3 years ago
A suitcase (mass m = 18 kg) is resting on the floor of an elevator. The part of the suitcase in contact with the floor measures
Sindrei [870]

Answer:

P=2736 Pa

Explanation:

According to Newton we have that:

∑F=m*a\\

A force is exerted by the elevator to the suitcase, according to 3th Newton's law an equal force but in the opposite direction will appeared on the suitcase, that is:

∑F=m*g+m*a=m*(g+a)

F=205.2N

We know that the pressure is given by:

P=\frac{F}{A}\\P=\frac{205.2N}{(0.50m)*(0.15m)}\\P=2736N/m^2=2736Pa

6 0
3 years ago
Denial cycled at 6 mph for 0.8 h. Then he jogged at 2 mph for
dexar [7]
<h3>Deniel's average speed for the total</h3><h3>distance is 3.6 mph</h3>

Average speed is difined as the total distance travelled divided by the total time required to cover the distance. Mathematically, it is expressed as:

Ave. Speed = \frac{Total distance }{Total time}

To obtain the average speed of Daniel, we shall determine the distance travelled in each case. This is illustrated below:

<h3>Case 1:</h3>

Speed 1 (S₁) = 6 mph

Time 1 (t₁) = 0.8 h.

<h3>Distance 1 (D₁) =? </h3>

Speed = \frac{Distance}{Time} \\\\S_{1}  = \frac{D_{1}}{t_{1}} \\\\6 = \frac{D_{1}}{0.8}

Cross multiply

D₁ = 6 × 0.8

<h3>D₁ = 4.8 mile</h3>

<h3>Case 2:</h3>

Speed 2 (S₂) = 2 mph

Time 2 (t₂) = 1.2 h.

<h3>Distance 2 (D₂) =? </h3>

S_{2} = \frac{D_{2}}{t_{2}}\\\\2 = \frac{D_{2}}{1.2}

Cross multiply

D₂ = 2 × 1.2

<h3>D₂ = 2.4 mile </h3>

Next, we shall determine the total time. This can be obtained as follow:

Time 1 (t₁) = 0.8 h.

Time 2 (t₂) = 1.2 h.

<h3>Total time (T) =? </h3>

T = t₁ + t₂

T = 0.8 + 1.2

<h3>T = 2 h</h3>

Next, we shall determine the total distance. This can be obtained as follow:

Distance 1 (D₁) = 4.8 mile

Distance 2 (D₂) = 2.4 mile

<h3>Total distance (D) =?</h3>

D = D₁ + D₂

D = 4.8 + 2.4

<h3>D = 7.2 mile</h3>

Finally, we shall determine the average speed of Daniel. This can be obtained as follow:

Total time = 2 h

Total distance  = 7.2 mile

<h3>Average speed =?</h3>

Ave. speed = \frac{Total distance }{Total time} \\\\Ave. speed = \frac{7.2 }{2}

<h3>Average speed = 3.6 mph</h3><h3 />

Therefore, the average speed of Daniel is 3.6 mph

Learn more: brainly.com/question/680492

5 0
2 years ago
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