# Tag Info

1

Neutrons have almost the same mass as protons and the unit of atomic mass is (at the moment: see footnote) $\frac{1}{12}^{th}$ of the mass of a carbon 12 nucleus. The mass of nucleons varies a little depending on which nucleus they belong to, but the difference (the binding energy) from their mass when free nucleons is small. So, to a good approximation, the ...

16

updated calculations - based on neutrino energy escaping and vapor inhalation risk Your math is close but not quite right. First - the number of tritium atoms. There are 1000/(16+3+3) = 45 moles (as you said) This means there are 45*2*$N_A$ = $5.5 \cdot 10^{25}$ atoms of Tritium Now the half life is 12.3 years or 4500 days, that is $3.9\cdot 10^8$s. ...

2

Arrows and paintballs go about the same speed, 200-300 feet per second. In episode 109, Mythbusters confirmed a professional ninja can block an arrow with a sword. It's plausible. However, distance is going to make a difference. I don't have the episode to check how far away the archer was, but in your question 24 feet (8 meters) is really close. It ...

0

As always in this sort of subject, you should consider Mythbusters, not just mention it. https://www.youtube.com/watch?v=2qY0DA7DG9s And the answer is pretty much, no you can't. It's reaction time that's the problem.

7

Correct me if I'm wrong, I believe that from a paintball gun when shooting there is no smoke, vapour or other visible exhaust and not even recoil. No visible signal. The dodger must rely on sound. Sound reaching the ears. The speed of sound in air is around $v=330\:\mathrm{m/s}$. Sound will propagate the $x=8\:\mathrm{m}$ and reach the dodger in ...

2

The time that the person has to dodge is $t=\frac{8 m}{160 m/s}=0.05 s$ So he has to move at a minimum speed of $v=\frac{0.50 m}{0.05 s}=10m/s$

1

As the Earth isn't a closed system with regard to other objects in the Solar System, including atomic particles, its momentum is affected by collisions. But if the collisions were inelastic (if the atomic particles were absorbed into elements of the crust and the atmosphere), the momentum of the atomic particles and the momentum of the Earth involved in the ...

0

It does affect the Earth, but at a rate so slow that the sun will expand into a red giant before that happens.

3

I looked up leap second in Wikipedia. It is a second added (usually) to clocks to keep them in sync with the atomic clock. Civilian clocks use Coordinated Universal Time (UTC), sometimes erroneously called Greenwich Mean Time (which no longer exists). Atomic clocks use International Atomic Time (TAI). UTC and TAI are in sync. Civilian clocks tick at the ...

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