That's a verrrrrry interesting question. Why has "life expectancy"
risen substantially in the US in the past Century ? Another way to
put it ... "Why has the average age of everybody gained so much ?".
Or "Why is there a greater part of the population living to more
advanced ages now, like into their 70s, 80s, and 90s ?"
I think most of us have the impression that the greatest advances
have been in treating the ailments and common problems of old
people, like arthritis, heart disease, cancer, general fitness and
nutrition etc. There has certainly been a lot of progress in those
areas, at the high end of the age distribution.
But . . .
It turns out that an even greater improvement in the statistics of
our longevity as a nation has resulted from great accomplishments
at the other end of the age spread ... the reduction in infant mortality,
and the conquest of diseases that killed great numbers of children
in the early 20th Century: Measles, mumps, whooping cough, flu,
chicken pox, diphtheria, rheumatic fever, even polio. Each of these
was a dreaded killer of children 100 years ago. By the time I was
a kid, they were rites of passage ... everybody gottum, got better,
and returned to school. And now, you hardly ever hear about
somebody getting any of these, and if there are a few cases in
the same year and in the same city, it's a big deal. They've been
largely wiped out. So there are far fewer childhood deaths than
there used to be, puling down the nationwide average lifespan.
Answer:
The second one a part of it heats up Earth's land and water equally.
Explanation:
Hope this help!!!
Answer:
The value is 
Explanation:
From the question we are told that
The speed of the marathon runner is 
The distance from the distance from the finish is 
The speed of the bird is 
Generally the time taken for the runner to reach the finish is mathematically represented as
So the distance covered by the bird is
Given: The mass of stone (m) = 0.5 kg
Raised from heights (h₁) = 1.0 m to (h₂) = 2.0 m
Acceleration due to gravity (g) = 9.8 m/s²
To find: The change in potential energy of the stone
Formula: The potential energy (P) = mgh
where, all alphabets are in their usual meanings.
Now, we shall calculate the change in potential energy of the stone
Δ P = P₂ - P₁ = mg (h₂ - h₁)
or, = 0.5 kg ×9.8 m/s² ×(2.0 m - 1.0 m)
or, = 4.9 J
Hence, the required change in the potential energy of the stone will be 4.9 J
