Ask question

Ask question

All categories

3 years ago

6

You are driving along a highway at 35.0 m/s when you hear the siren of a police car approaching you from behind and you perceive

the frequency as 1370 Hz. You are relieved that he is in pursuit of a different speeder when he continues past you, but now you perceive the frequency as 1330 Hz. What is the speed of the police car? The speed of sound in air is 343 m/s.

1 answer:

swat323 years ago

6 0

Answer:

Explanation:

Given

Apparent frequency $f'=1370\ Hz$

Velocity of sound $v=343\ m/s$

speed of observer $v_o=35\ m/s$

Using Doppler effect Apparent frequency when source is approaching is given by

$f'=f(\frac{v-v_0}{v-v_s})$

$1370=f(\frac{343-35}{343-v_s})---1$

Apparent frequency when source moves away from observer

$f''=f(\frac{v+v_0}{v+v_s})$

$1330=f(\frac{343+35}{343+v_s})---2$

Divide 1 and 2 we get

$\frac{f'}{f''}=\frac{\frac{343-35}{343-v_s}}{\frac{343+35}{343+v_s}}$

$\frac{1370}{1330}=\frac{343-35}{343-v_s}\times \frac{343+v_s}{343+35}$

$v_s=40\ m/s$

Thus speed of sound of police car is 40 m/s

You might be interested in

A Ferris wheel on a California pier is 27 m high and rotates once every 32 seconds in the counterclockwise direction. When the w

Leto [7]

A) 140 degrees

First of all, we need to find the angular velocity of the Ferris wheel. We know that its period is

T = 32 s

So the angular velocity is

$\omega=\frac{2\pi}{T}=\frac{2\pi}{32 s}=0.20 rad/s$

Assuming the wheel is moving at constant angular velocity, we can now calculate the angular displacement with respect to the initial position:

$\theta= \omega t$

and substituting t = 75 seconds, we find

$\theta= (0.20 rad/s)(75 s)=15 rad$

In degrees, it is

$15 rad: x = 2\pi rad : 360^{\circ}\\
x=\frac{(15 rad)(360^{\circ})}{2\pi}=860^{\circ} = 140^{\circ}$

So, the new position is 140 degrees from the initial position at the top.

B) 2.7 m/s

The tangential speed, v, of a point at the egde of the wheel is given by

$v=\omega r$

where we have

$\omega=0.20 rad/s$

r = d/2 = (27 m)/2=13.5 m is the radius of the wheel

Substituting into the equation, we find

$v=(0.20 rad/s)(13.5 m)=2.7 m/s$

6 0

3 years ago

The equation below is for potassium oxide.

ValentinkaMS [17]

Answer: The ratio of atoms of potassium to ratio of atoms of oxygen is 4:2

Explanation:

According to the law of conservation of mass, mass can neither be created nor be destroyed, and remains conserved. The mass of products must be same as that of the reactants.

Thus the number of atoms of each element must be same on both sides of the equation so as to keep the mass same and thus balanced chemical equations are written.

K exists as atoms and oxygen exist as molecule which consists of 2 atoms. The ratio of number of atoms on both sides of the reaction are same and thus the ratio of atoms of potassium to ratio of atoms of oxygen is 4:2.

5 0

3 years ago

Read 2 more answers

A 4.44 l container holds 15.4 g of oxygen at 22.55°c. what is the pressure?

padilas [110]

We will use the ideal gas equation:
PV = nRT, where n is moles and equal to mass / Mr
P = mRT/MrV
P = 15.4 x 8.314 x (22.55 + 273) / 32 x 4.44
P = 266.3 kPa

5 0

3 years ago

The angle a vector makes with the x-axis of a coordinate system must be what size in order to make one or more of its components

Aneli [31]

If only 1 option is correct then it is (D)
All the others can also make one component negative, all depends how u measured the angle.
all the best

3 0

3 years ago

Read 2 more answers

In a ballistics test, a 24 g bullet traveling horizontally at 1200 m/s goes through a 31-cm-thick 320 kg stationary target and e

Zanzabum

Answer:

The velocity is $v_t = 0.02175 \ m/s$

Explanation:

From the question we are told that

The mass of the bullet is $m_b = 0.024 \ kg$

The initial speed of the bullet is $u_b = 1200 \ m/s$

The mass of the target is $m_t = 320 \ kg$

The initial velocity of target is $u_t = 0 \ m/s$

The final velocity of the bullet is is $v_b = 910 \ m/s$

Generally according to the law of momentum conservation we have that

$m_b * u_b + m_t * u_t = m_b * v_b + m_t * v_t$

=> $0.024 * 1200 + 320 * 0 = 0.024 * 910 + 320 * v_t$

=> $v_t = 0.02175 \ m/s$

3 0

3 years ago