The diagram is missing; however, we know that the intensity of a sound wave is inversely proportional to the square of the distance from the source:
where I is the intensity and r is the distance from the source.
We can assume for instance that the initial distance from the source is r=1 m, so that we put
The intensity at r=3 m will be
Therefore, the sound intensity has decreased by a factor
.
Answer:
&
Explanation:
Given:
- interior temperature of box,
- height of the walls of box,
- thickness of each layer of bi-layered plywood,
- thermal conductivity of plywood,
- thickness of sandwiched Styrofoam,
- thermal conductivity of Styrofoam,
- exterior temperature,
<u>From the Fourier's law of conduction:</u>
....................................(1)
<u>Now calculating the equivalent thermal resistance for conductivity using electrical analogy:</u>
.....................(2)
Putting the value from (2) into (1):
is the heat per unit area of the wall.
The heat flux remains constant because the area is constant.
<u>For plywood-Styrofoam interface from inside:</u>
&<u>For Styrofoam-plywood interface from inside:</u>
In that case, their momentum must be equal.
So, m1v1 = m2v2
20 * 20 = 40 * v2
v2 = 400 / 40
v2 = 10
In short, Your Answer would be: 10 m/s
Hope this helps!