The Pony Express
Chapter 1
At A Nation's Crisis
The Pony Express was the first rapid transit and the first fost mail line across the continent from the Missouri River to the Pacific Coast. It was a system
by means of which messages were carried swiftly on horseback across the plains and deserts, and over the mountains of the far West It brought the
Adontic coost and the Pacific slope ten days nearer to each other.
It had a brief existence of only sixteen months and was supplanted by the transcontinental telegraph. Yet it was of the greatest importance in
binding the East and West together at a time when overland travel was slow and cumbersome, and when a great national crisis made the rapid
communication of news between these sections an imperative necessity.
The Pony Express marked the highest development in overland travel prior to the coming of the Pacific railroad, which it preceded nine years.
It, in fact, proved the feasibility of a transcontinental road and demonstrated that such a line could be built and operated continuously the year
around-a feat that had always been regarded as impossible.
The operation of the Pony Express was a supreme achievement of physical endurance on the part of man and his ever faithful companion, the
horse. The history of this organization should be a lasting monument to the physical sacrifice of man and beast in an effort to accomplish
something worthwhile. Its history should be an enduring tribute to American courage and American organizing genius.
Read this line from the Pony Express excerpt
It hod a brief existence of only sixteen months and was supplanted by the transcontinental telegraph.
Based on the corres, what does the word "supplanted" mean? (5 points)
Defeated
Joined
Replaced
Os
Oo
Unearthed
Answer:
Being a plane mirror the Image is formed 3 metres beyond the mirror . So total distance is 3+3 = 6metres
To solve this problem we will apply the concepts related to wavelength, as well as Rayleigh's Criterion or Optical resolution, the optical limit due to diffraction can be calculated empirically from the following relationship,
Here,
= Wavelength
d= Diameter of aperture
= Angular resolution or diffraction angle
Our values are given as,
The frequency of the sound is 
The speed of the sound is 
The wavelength of the sound is
Here,
v = Velocity of the wave
f = Frequency
Replacing,
The diffraction condition is then,
Replacing,
d = 0.24 m
Therefore the diameter should be 0.24m
<span>When t=0, v=0, d=0
When t=tf, v=41m/s, d=3.5m
We have 2 formulas – the ones corresponding to uniformly accelerated linear movement:
vf=a*t+vo
d=(1/2)*a*t^2+vo*t
Let’s put the data in the formulas:
41m/s=a*t+0=a*t
3.5m=(1/2)*a*t^2+0*t=1/2*a*t^2
You can use a variety of methods to find t and a. I will choose substitution.
t=(41m/s)/a
3.5m=(1/2)*a*((41m/s)/a)^2=(1/2)*a*(41m/s)^2/a^2=(1/2)*(41m/s)^2/a
a=(1/2)*(41m/s)^2/(3.5m)=(1/2)*41^2(m^2/s^2)/(3.5m) a=41^2(m/s^2)/( 2*3.5)=240m/s^2</span>
