<span>Glass is transparent meaning light passes through it and therefore you can see through it, but some light reflects back and if the surface is very smooth as glass often is then the light reflected back can be seen as a reflected image.</span>
Answer:
a

b

Explanation:
From the question we are told that
The mass of the rock is 
The length of the small object from the rock is 
The length of the small object from the branch 
An image representing this lever set-up is shown on the first uploaded image
Here the small object acts as a fulcrum
The force exerted by the weight of the rock is mathematically evaluated as

substituting values


So at equilibrium the sum of the moment about the fulcrum is mathematically represented as

Here
is very small so
and 
Hence

=> 
substituting values


The mechanical advantage is mathematically evaluated as

substituting values


Answer:
fb = 240.35 Hz
Explanation:
In order to calculate the beat frequency generated by the first modes of each, organ and tube, you use the following formulas for the fundamental frequencies.
Open tube:
(1)
vs: speed of sound = 343m/s
L: length of the open tube = 0.47328m
You replace in the equation (1):
Closed tube:

L': length of the closed tube = 0.702821m

Next, you use the following formula for the beat frequency:

The beat frequency generated by the first overtone pf the closed pipe and the fundamental of the open pipe is 240.35Hz
Answer:
Explanation:
The rate of change in volume is proportional to the surface area:
dV/dt = kA
Integrating:
V = kAt + C
At t=0, V = s, so:
s = kA(0) + C
C = s
Therefore:
V = kAt + s