Answer:
-3.396 m/s or 3.465 m/s
Explanation:
v = Speed of sound in air = 343 m/s
 = Relative speed of the singer
 = Relative speed of the singer
f = Observed frequency
f' = Actual frequency
1% change can mean 
From the Doppler effect equation we have

The velocity is -3.396 m/s
when 

The velocity is 3.465 m/s
 
        
             
        
        
        
That is b. hope this helps cx
        
             
        
        
        
The scale in N, reading if the elevator moves upward at a constant speed of 1.5 m/s^2 is 862.5 N.
weight of man = 75kg 
speed of elevator, a = 1.5 






So, the scale reading in the elevator is greater than his 862.5 N weight. This indicates that the person is being propelled upward by the scale, which it must do in order to do so, with a force larger than his weight. According to what you experience in quickly accelerating or slowly moving elevators, it is obvious that the faster the elevator acceleration, the greater the scale reading.
Speed can be defines as the pace at which the position of an object changes in any direction.  Since speed simply has a direction and no magnitude, it is a scalar quantity.
Learn more about speed here:- 
brainly.com/question/19127881
#SPJ4
 
        
             
        
        
        
Explanation:
The solution is be found in the attachment.
 
        
             
        
        
        
Answer:

Explanation:
Ok, the average speed can be calculate with the next equation:
 (1)
   (1)
Basically the car cover the same distance "d" two times, but at different speeds, so:

and the total time would be the time t1 required to go from A to B plus the time t2 required to go back from B to A:

From basic physics we know:

so:


Using the previous information in equation (1)

Factoring:
 (2)
   (2)
Finally, replacing the data in (2)
