Answer:
a. wavelength of the sound, 
b. observed frequecy, 
Given:
speed of sound source, 
= 80 m/s
speed of sound in air or vacuum, 
= 343 m/s
speed of sound observed, 
= 0 m/s
Solution:
From the relation:
v = 
(1)
where
v = velocity of sound
= observed frequency of sound
= wavelength
(a) The wavelength of the sound between source and the listener is given by:
(2)
(b) The observed frequency is given by:
(3)
Using eqn (2) and (3):
Retrograde. Planets seem to move forward and then backward sometimes. This is really because we pass them as we move in our orbit but astronomers wanted to try to describe the solar system with earth at the center so elaborate models were employed.
The correct option is (b) 5n
As a result, there is a net downward force of 5N operating on the object.
The resultant force is the force that results from adding the vector sums of all the forces operating on an item. The combined action of all the acting forces on the object produces the same effect as the resulting force. When determining the resulting force, the direction of the forces must be taken into account.
Given;
The northward force is Fn = 10N
The southward force is Fs = 15N
Required;
The net force on the mobile phone is Fnet = ?N
The object's weight exerts downward pressure, and upward resistance exerts upward pressure. The vector sum of these two forces will be the net force.
Fnet = Fs - Fn (Considering the direction downward as positive)
Fnet= 15N - 10N
Fnet = 5N
As a result, there is a net downward force of 5 N operating on the object.
Learn more about the Force with the help of the given link:
brainly.com/question/7362815
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