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:
We know that the speed of sound is 343 m/s in air
we are also given the distance of the boat from the shore
From the provided data, we can easily find the time taken by the sound to reach the shore using the second equation of motion
s = ut + 1/2 at²
since the acceleration of sound is 0:
s = ut + 1/2 (0)t²
s = ut <em>(here, u is the speed of sound , s is the distance travelled and t is the time taken)</em>
Replacing the variables in the equation with the values we know
1200 = 343 * t
t = 1200 / 343
t = 3.5 seconds (approx)
Therefore, the sound of the gun will be heard at the shore, 3.5 seconds after being fired
Complete Question
A truck going 15 km/h has a head-on collision with a small car going 30 km/h. Which statement best describes the situation?
A. the truck has the greater change of momentum because it has the greater mass
B. the car has the greater change of momentum because it has the greater speed
C. neither the car nor the truck changes its momentum in the collision because momentum is conserved
D. they both have the same change in magnitude of momentum because momentum is conserved
E. none of the above is necessarily true
Answer:
D. They both have the same change in magnitude of momentum because momentum is conserved
Explanation:
In order to get a good understanding of the solution above we define some
concetps
Momentum
This is defines quantified motion and can be mathematically represented as
Momentum = Mass of the body × Velocity of the body
According to the Law of conservation of momentum states that when two particles collide together in a system that is being isolated that their total momentum before and after their collision is equal this means that the momentum lost by the truck would be the same as the momentum gained by the small car
C. A survey is asking people what they think is the answer.
The magnitude of the average force exerted by the seat belt on the dummy is 224N .
<h3>What is an average force ?</h3>
The average force is the force produced by an object moving over a specific period of time at a given rate of speed, or velocity. This velocity is not instantaneous or precisely measured, as the word "average" indicates.
<h3>Briefing:</h3>
mass of the dummy (m) = 80kg
velocity of the dummy (v) = 28 m/s
time (t) = 10 seconds
Average force exerted (F)
To calculate the average force;
According to the formula;
F = (m × v) ÷ t
Where;
F represents the force exerted
m represents the mass of the dummy
v represents the velocity
t represents the time
F = m * v/t
F = 80 *28/10
F = 224
F = 224 N
The force exerted by the seat belt on the dummy is 224N .
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