Answer:
25 m/s
Explanation:
from the question you van see that some detail is missing, however i found this same question using internet search engines on: 'https://www.chegg.com/homework-help/questions-and-answers/light-rail-passenger-trains-provide-transportation-within-cities-speed-slow-nearly-constan-q5808369'
here is the complete question:
'Light-rail passenger trains that provide transportation within and between cities speed up and slow down with a nearly constant (and quite modest) acceleration. A train travels through a congested part of town at 7.0m/s . Once free of this area, it speeds up to 12m/s in 8.0 s. At the edge of town, the driver again accelerates, with the same acceleration, for another 16 s to reach a higher cruising speed. What is the final Speed?'
SOLUTION
initial speed (u) = 7 m/s
final speed (v) = 13 m/s
initial acceleration time (t1) = 8 s
final acceleration time (t2) = 16 s
what is the higher cruising speed?
acceleration = 
acceleration = 
= 0.75 m/s^{2}
since the train accelerates at the same rate, the increase in speed will be = acceleration x time (t2)
= 0.75 x 16 = 12 m/s
therefore the higher cruising speed = increase in speed + initial speed
= 12 + 13 = 25 m/s
Answer:
decibels (dB)
Explanation:
The sound intensity level is a quantity derived from the sound intensity.
The intensity of a wave is defined as the power of the source of the wave divided by the area through which the power of the wave is spread, mathematically:
where
P is the power of the source
is the surface area over which the wave spreads (assuming that the wave propagates in all directions, it corresponds to the surface area of a sphere of radius 
, where r is the distance between the source of the wave and the observer)
For sound waves, the intensity is often expressed using another unit, called decibel (dB), defined as follows:
where
is the sound intensity level in decibels
I is the intensity of the sound wave
is the threshold intensity of a sound that a person can normally hear.
The characteristics of the diffraction phenomenon allow to find the result for the shape of the points of light that you pass the tree is:
-
The shape of the dots is circular because it is in the range of far-field diffraction.
Diffraction is the phenomenon where the undulatory part of the light becomes evident, it is the interference of the waves that make up each ray of light, for this phenomenon to occur it must be fulfilled that the wavelength is of the order of the space where pass the light.
In the leafy tree it has many leaves, but there are spaces between them, some of these spaces are small and it fulfills the diffraction condition, therefore we see bright spots and not a continuous shadow.
Diffraction can be classified depending on the distance to the observer:
- Near field or fresnel. In this case the distance from the observer is small and we can see the shape of the object that creates the diffraction.
- Far field or Fraunhoger. In this case the distance between the obstacle (leaves) and the person is great, here the information on the shape of things is lost and we have two observable forms. Lines for the case of slits and circles for the case of objects with a closed shape.
In this case, the distance from the leaves to the observer is large, therefore we are in the case of far-field diffraction and since the edge of the leaves that forms the diffraction is closed, the observable shape is a circle.
In conclusion using the characteristics of the diffraction phenomenon we can find the result for the shape of the points of light that pass the tree is:
-
The shape of the dots is circular because it is in the range of far-field diffraction.
Learn more about diffraction here: brainly.com/question/20140459
