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test post march 15

| Friday, March 14, 2014

test post march 15



test post march 15

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Some Physics One-Liners

| Wednesday, March 5, 2014

Ever since humans have studied the inner workings of the natural world, mathematical equations have been used to accurately describe what was happening. That's why physics, with its attempts to describe motion, has come up with many different mathematical formulae for various phenomena. For this random post, here are a few one-liners that involve physics concepts, based on common phrases and pop culture. can you name the concepts, or say the original line? Some are a bit easier than the others. :)


  1. With great power comes either great work, or a very short time to do some work. 

  2. M A be the Force be with you.

  3. Dead or alive, your cat's coming with me.

  4. Go ahead, make my 8.64x104 seconds.

  5. I feel the need—the need for dx/dt!

Anything else you can think of? Post it in the comments below!



Some Physics One-Liners

The Physics Behind the Nonsense: Pinocchio's Nose and Earth Orbit

| Sunday, March 2, 2014

The Question


As I was watching videos on my YouTube account, this SciShow video was among the recommendations. Now, I love reading the comments as much as watching the video itself; there is usually a comment that simply makes me roll over laughing. Every so often though, something golden comes up, like the following question which has become one of the top comments.


If Pinocchio's nose is 1 inch long, how many lies does Pinocchio need to tell to get into near earth orbit, remembering that at some point Pinocchio will fall over because his nose is too long?


The Short Answers


First, we need to assume the diameter of Pinocchio's nose, otherwise the calculations can have many different answers. So to make things easier, we will set the diameter to 0.50 inches (1.27 cm). Another assumption we will make is that Earth's gravitational field strength is uniform for the distances covered. A short calculation will reveal that this assumption is a very good approximation, since the value of g at 160 km above the earth is 95% of that on the surface.


There are many possible answers, depending on how Pinocchio is positioned. If he was lying down with his nose pointing up, then one of the following would occur.


  • It would take around 6.5 million lies for his nose to get to low earth orbit, assuming the nose is massless.

  • If the mass of the nose changes with length, his face gets crushed after ___ lies.

If Pinocchio was standing up with his nose level to the ground, either of the following may happen


  • About 56 million lies are required to get to low earth orbit. This assumes the nose is massless.

  • If the mass of the nose changes with length, he falls over somewhere between 700 and 800 lies. As he continues to lie, his nose will keep growing until it surrounds the earth, hugging the ground.

These are all the simple answers possible, and we'll look at why on the next page.



The Long Answers


For the simplest possible answer, we will ignore everything else and just look at the length of the nose needed to reach low Earth orbit, which sits at 160 km (100 miles). If Pinocchio lies down, his nose only needs to travel 160 km to get to low earth orbit.


image of nose going vertically out of atmosphere


Since an inch is defined to be 2.54 cm in length, we convert it and use the value to find the number of lies needed.


Nose \quad length \quad increment \quad per \quad lie = 2.54 cm = 2.54 \times 10^-5 km


Number \quad of \quad Lies = 160 \quad km \times \frac1 \quad lie2.54 \times 10^-5 \quad km


Number \quad of \quad Lies = 6.53 \times 10^6 \quad lies


The situation is slightly different when Pinocchio's nose is horizontal to the ground. In this case, his nose has to travel 1434 km, since it has to go through a thicker later of atmosphere, as shown below.


image


Calculating the number of lies is pretty straightforward though.


Number \quad of \quad lies = 1434 \quad km \times \frac1 \quad lie2.54 \times 10^-5 \quad km


Number \quad of \quad lies = 5.65 \times 10^7 \quad lies


For the other questions, let's assume that Pinocchio is still a marionette made of wood. Most types of wood have a density of 700 kilograms per cubic metre, which is about half that of flesh. We can assume that Pinocchio has the same mass as an 8-year-old boy who has twice his volume. Since an average 8-year-old would have a mass of 30 kg, Pinocchio should have the same mass. Furthermore, Pinocchio's nose should be 300 g in mass and 3.0 cm in length.


This


 


asd


Sources



The Physics Behind the Nonsense: Pinocchio's Nose and Earth Orbit