The original frequency of horn of Car A is 1071 Hz.
Explanation:
Doppler effect describes the change in the frequency of sound waves with respect to the observer. As the sound waves emitted from a source need to travel the air medium to reach observer, it will undergo loss in energy. So there will be change in its frequency compared to original frequency. Depending upon the direction of travel of source and observer the shifting of frequency will vary.

Here vo is the observer velocity and vs is the velocity of the source. So Vo = 15 m/s as car B is the observer and Vs = 35 m/s as car A is the source. And f is the frequency of sound wave at source that is car A.
Similarly, the doppler shift in frequency is the frequency of sound heard by car B which is f' = 1140 Hz. And v is the speed of sound that is v = 343 m/s
1140 = 
f = 1140/1.0649= 1071 Hz.
Thus, the original frequency of horn of Car A is 1071 Hz.
Answer:
, inside the plane
Explanation:
We need to calculate the magnitude and direction of the magnetic field produced by each wire first, using the formula

where
is the vacuum permeability
I is the current
r is the distance from the wire
For the top wire,
I = 4.00 A
r = d/2 = 0.105 m (since we are evaluating the field half-way between the two wires)
so

And using the right-hand rule (thumb in the same direction as the current (to the right), other fingers wrapped around the thumb indicating the direction of the magnetic field lines), we find that the direction of the field lines at point P is inside the plane
For the bottom wire,
I = 5.90 A
r = 0.105 m
so

And using the right-hand rule (thumb in the same direction as the current (to the left), other fingers wrapped around the thumb indicating the direction of the magnetic field lines), we find that the direction of the field lines at point P is also inside the plane
So both field add together at point P, and the magnitude of the resultant field is:

And the direction is inside the plane.
V^2 = u^2 + 2gr, where v - speed, u - initial speed=0, r - displacement (or height)
v^2 = 0 + 2*10*5.4
v = 10.2 m/s
Answer:
15.64 KN
Explanation:
mass of the elevator cab with a single occupant= 2300 kg
acceleration relative to the cab
= 6.80 m/s^2
acceleration of the coin relative to the cab in the opposite direction of motion of cab so we can consider it as a= -6.80 m/s^2
The acceleration of elevator cab relative to the ground 
now we can say that

=-6.80+ a_{eg}= -9.8
[tex]a_{eg}=-9.8+6.80=-3.8
The forces that act on elevator cab are tension and gravitational, applying newtons second law
T- mg= ma_{eg}
Then the tension in the cable is
T= 2300(-3.8)+2300×9.8= 15640 N= 15.64 KN
therefore tension in the string will be 15.64 KN