185 reputation
19
bio website Grieu
location
age
visits member for 3 years, 3 months
seen 10 hours ago

I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.

Feel free to edit my answers to fix obvious errors, or improve them on expression (I'm not a native English speaker).


12h
revised Dropping a weight onto a spring scale
The method is doomed
12h
revised Dropping a weight onto a spring scale
Mention we should not trust the result
13h
revised Dropping a weight onto a spring scale
Explain the case h=0
13h
revised Dropping a weight onto a spring scale
Give hypothesis
13h
revised Dropping a weight onto a spring scale
Expand with numeric values and comparison to other answer giving an approximation
15h
awarded  Teacher
15h
answered Dropping a weight onto a spring scale
15h
comment Dropping a weight onto a spring scale
Correction: if we make $h=0$, we should obtain $m=2M$.
17h
comment Dropping a weight onto a spring scale
If we make $h=0$, the displayed mass$$m=\sqrt{2\;k\;h\;M\over g}$$ is $m=0$, when it should be $m=M$ (what is displayed when we delicately put the weight on the scale, as we should). Also this solution does not account for the statement's fact that the display $m$ is more than $M$ for all $h>0$. So this can't be exactly right. Perhaps it is a valid approximation in some unstated domain, like $$h\gg{M\;g\over k}$$PS: what a pain that the notation makes $m>M$.
Dec
13
comment Will a bullet dropped and a bullet fired from a gun horizontally REALLY hit the ground at the same time when air drag is taken into account?
Problem with this line of thought is that from an experimental standpoint, and when the bullet starts from an height from ground commensurate to a man's size, the effect of $F_y$ on the time it takes for the bullet to reach ground is negligible in both the case of the bullet dropped, and the case of the bullet fired. In the first case, the overwhelming factor is the drop height. In the second case, that's the (practically unavoidable) vertical component of the bullet's initial velocity, and the height.
Dec
10
awarded  Autobiographer
Nov
16
awarded  Announcer
Oct
15
awarded  Commentator
Oct
15
revised Reproductibility of the effects described in US patent 8,419,919
My description now focus a single remarkable effect
Oct
15
comment Reproductibility of the effects described in US patent 8,419,919
I concur on current claims of cold fusion as a practical way to produce non-trivial amounts of energy. However the exposition in the patent I refer to does not describe any production of energy (much to the contrary: a lot is absorbed).
Oct
15
revised Reproductibility of the effects described in US patent 8,419,919
Polish question per comment
Oct
14
accepted What makes a wrist-energized gyroscope rotate faster?
Oct
14
revised Reproductibility of the effects described in US patent 8,419,919
Clarify by removing "public", which was interpreted as "in front of an audience"
Oct
14
comment Reproductibility of the effects described in US patent 8,419,919
@CuriousOne: By publicly I meant: that can been reported; by opposition to classified. I'll fix the question.
Oct
14
asked Reproductibility of the effects described in US patent 8,419,919