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Cliffg37
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I am reading the book "The Daughter of Sherlock Holmes." I have loved holmes since I was 11 years old, and this book that was published two years ago is very well written and carries on in the spirit of Sir Arthur and his fictional detective. I am only a few chapters in but I am liking it.

Without offering any spoilers an issue is raised of how far something will fall in 5 seconds. It is pointed out that things fall at 32 feet/second. so 5 seconds times 32 feet per second would equal 160 feet. I guess the author, who is well known and has published several books didn't bother to check his physics.

Things do not fall at 32 feet/second. Falling objects accelerate at 32 feet/second squared. That word "Squared" is just one word and who really cares about that. Well in five seconds an object dropped from a motionless position would actually fall 400 feet.

The author made the mistake of using distance=velocity times time. A fine formula that I do teach my students. But it is useless in an accelerating situation. He should have used Distance = 1/2 acceleration times time squared.

Truthfully not the first one I've seen make this elementary error.

Sir Isaac is rolling over in his grave.

Class Dismissed.
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Jonathan Townsend
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The originals were engaging stories. How's the writing?
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Cliffg37
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Only 7 chapters in, but the writing is pretty good. The storytelling is well done too.
Magic is like Science,
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arthur stead
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While on tour in Europe, I was very fortunate to obtain tickets, purely by chance, to see Jeremy Brett and David Burke (Dr. Watson) in their 2-man Sherlock Holmes stage play in London’s West End. It was magnificent! A once-in-a-lifetime experience.

Speaking of an older Sherlock, the movie Mr. Holmes featuring Ian McKellan is beautifully done and superbly acted. Have you seen it, Cliff?
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R.S.
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Quote:
On Aug 29, 2019, Cliffg37 wrote:

Without offering any spoilers an issue is raised of how far something will fall in 5 seconds. It is pointed out that things fall at 32 feet/second. so 5 seconds times 32 feet per second would equal 160 feet. I guess the author, who is well known and has published several books didn't bother to check his physics.

Things do not fall at 32 feet/second. Falling objects accelerate at 32 feet/second squared. That word "Squared" is just one word and who really cares about that. Well in five seconds an object dropped from a motionless position would actually fall 400 feet.

The author made the mistake of using distance=velocity times time. A fine formula that I do teach my students. But it is useless in an accelerating situation. He should have used Distance = 1/2 acceleration times time squared.



This always confused me. Isn't there a point at which the acceleration eventually stabilizes and objects will fall at a constant speed??

Thanks Cliff.
Ron
"It is error only, and not truth, that shrinks from inquiry." Thomas Paine
balducci
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For R.S.:

"Near the surface of the Earth, an object in free fall in a vacuum will accelerate at approximately 9.8 m/s2, independent of its mass. With air resistance acting on an object that has been dropped, the object will eventually reach a terminal velocity, which is around 53 m/s (195 km/h or 122 mph[4]) for a human skydiver. The terminal velocity depends on many factors including mass, drag coefficient, and relative surface area and will only be achieved if the fall is from sufficient altitude. A typical skydiver in a spread-eagle position will reach terminal velocity after about 12 seconds, during which time he will have fallen around 450 m (1,500 ft)."

https://en.wikipedia.org/wiki/Free_fall

The page at the link contains lots of other interesting tidbits.
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balducci
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Quote:
On Aug 29, 2019, Cliffg37 wrote:
I am reading the book "The Daughter of Sherlock Holmes." I have loved holmes since I was 11 years old, and this book that was published two years ago is very well written and carries on in the spirit of Sir Arthur and his fictional detective. I am only a few chapters in but I am liking it.

Without offering any spoilers an issue is raised of how far something will fall in 5 seconds. It is pointed out that things fall at 32 feet/second. so 5 seconds times 32 feet per second would equal 160 feet. I guess the author, who is well known and has published several books didn't bother to check his physics.

As you haven't finished the book yet, I wonder whether the mistake you noticed will come back and prove significant in some fashion? Maybe the author is well aware of the error, and the incorrect explanation serves a purpose in the story later on.
Make America Great Again! - Trump in 2020 ... "We're a capitalistic society. I go into business, I don't make it, I go bankrupt. They're not going to bail me out. I've been on welfare and food stamps. Did anyone help me? No." - Craig T. Nelson, actor.
landmark
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Balducci, that reminds me of the great Gary Larsen cartoon where a distraught Einstein is at his blackboard and you see crossed out, E=MC^3 and E=MC^10 and E=MC^5. And behind him is a cleaning woman straightening out his messy desk, and she says, "Well I guess that squaaaares everything away."
Cliffg37
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On Aug 30, 2019, arthur stead wrote:
Speaking of an older Sherlock, the movie Mr. Holmes featuring Ian McKellan is beautifully done and superbly acted. Have you seen it, Cliff?


I have Arthur,

I thought Sir Ian did an amazing job of taking a fictional character and showing us what he might be like if he were real. I basically loved the film.
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Cliffg37
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Quote:
On Aug 30, 2019, R.S. wrote:
This always confused me. Isn't there a point at which the acceleration eventually stabilizes and objects will fall at a constant speed??
Thanks Cliff.
Ron


Correct Ron, It is called Terminal Velocity. This is what happens after something has fallen for 5.4 seconds. We hit a speed of about 125 miles per hour. I say about becasue there are factors that alter it slightly (How hot is it, how humid is it, what altitude are you at) But at this point, the air pushing against you as you fall, exactly counters and matches the acceleration of gravity. You end up remaining at that speed until you, hit the ground, open a parachute, get caught by something etc.
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pegasus
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[/quote]

This always confused me. Isn't there a point at which the acceleration eventually stabilizes and objects will fall at a constant speed??

Thanks Cliff.
Ron [/quote]

Consider the analogy as Einstein did. Gravity and acceleration are equivalent forces. Therefore it is us and earth, and the air that is continually accelerating upwards, and the ‘falling’ person (is weightless) and therefore cannot be accelerating, and so is literally floating in space.
S2000magician
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Quote:
On Aug 30, 2019, R.S. wrote:
Quote:
On Aug 29, 2019, Cliffg37 wrote:
Without offering any spoilers an issue is raised of how far something will fall in 5 seconds. It is pointed out that things fall at 32 feet/second. so 5 seconds times 32 feet per second would equal 160 feet. I guess the author, who is well known and has published several books didn't bother to check his physics.

Things do not fall at 32 feet/second. Falling objects accelerate at 32 feet/second squared. That word "Squared" is just one word and who really cares about that. Well in five seconds an object dropped from a motionless position would actually fall 400 feet.

The author made the mistake of using distance=velocity times time. A fine formula that I do teach my students. But it is useless in an accelerating situation. He should have used Distance = 1/2 acceleration times time squared.

This always confused me. Isn't there a point at which the acceleration eventually stabilizes and objects will fall at a constant speed??

Thanks Cliff.

Not in a vacuum.

However, in the presence of air resistance, yes.
Cliffg37
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On Aug 30, 2019, S2000magician wrote:

Not in a vacuum.

However, in the presence of air resistance, yes.


The book takes place in 1914 or so where there is no concept of "outer space"

Should I make the obvious joke and say it sucks?

Seriously your point is well taken, but in the book, the object in question is dropped from the roof of a three story buiilding.
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Jonathan Townsend
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? Cliff, what do you mean concept of "outer space"? Was there no Newton, Maxwell, and (comes 1905) Einstein?

When there's a force of gravity things accelerate... oh - got you - it's a virtual world. Neat!
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Cliffg37
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In the 1920's we still did not understand that there was no air in space. Most people felt that there was air like here all the way up. Gravity was well studied by then, and Sir Isaac demonstrated far more than he should have been able to. His law of universal gravitation depends on him knowing the mass of the Earth. He made an incredibly accurate educated guess and hit it more or less on the nose.

From his study of light Einstein probably knew that space was empty, and by the time he died (1955) we all knew it. but in 1914 I doubt most people knew or even gave it a thought.

Olaus Roemer may or may not have know that space was empty when he used eclipses to measure the speed of light, but when Michaelson and Morely showed the speed of light on earth, Einstein parleyed both studies to conclude that the speed of light was constant, which led him to relativity

Bottom line: John and Jane public did not know until much later.
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S2000magician
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Quote:
On Aug 30, 2019, Cliffg37 wrote:
Quote:
On Aug 30, 2019, S2000magician wrote:
Not in a vacuum.

However, in the presence of air resistance, yes.

The book takes place in 1914 or so where there is no concept of "outer space"

Should I make the obvious joke and say it sucks?

Seriously your point is well taken, but in the book, the object in question is dropped from the roof of a three story buiilding.

You're familiar with The Barometer Story, no?
Animated Puppets
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With a female protagonist investigating, does this mean the maid did it?
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R.S.
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Thanks Balducci, Cliff, Pegasus, and Bill!

Ron
"It is error only, and not truth, that shrinks from inquiry." Thomas Paine
Jonathan Townsend
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Yes! Smile Thanks Bill!
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Cliffg37
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Quote:
On Aug 30, 2019, S2000magician wrote:

You're familiar with The Barometer Story, no?


Yes indeed, I know it well and tell it every year. It is very cool and I love it
Magic is like Science,
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