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May
13
awarded  Nice Answer
May
12
awarded  Yearling
Feb
8
revised What justifies dimensional analysis?
added 140 characters in body
Feb
8
revised What justifies dimensional analysis?
deleted 1775 characters in body
Feb
8
answered What justifies dimensional analysis?
Feb
5
comment Looking for the actual reason of refraction explained precisely without analogies
No one has mentioned Huygens' principle yet? It convinced me when I was 15 years old.
Jan
27
comment Is it possible for a physical object to have a irrational length?
The problem I see with your question is that you have defined a hypothetical caliper and are complaining when people are applying it to hypothetical objects. You can only measure physical objects with physical calipers, and hypothetical objects with hypothetical calipers.
Nov
18
awarded  Commentator
Nov
18
comment I'm having trouble understanding the dimensions of this falling body problem
Anyway, yes, the $5$ has dimensions of force per unit velocity = $\mathrm{N\:s\:m^{-1} = kg\:s^{-1}}$. This is no more unusual than if I were to say a thermometer's mercury level rises 2 millimeters whenever the temperature goes up by a degree Celsius, giving units of $\mathrm{m\:K^{-1}}$.
Oct
29
awarded  Editor
Oct
29
revised What does the wind speed have to be to blow away a person?
fixed links
Oct
29
suggested suggested edit on What does the wind speed have to be to blow away a person?
Jul
24
comment Can one make a ball rotate around a vertical axis using only a combination of horizontal axis rotations?
What is the exact text of the problem?
Jul
24
comment Can one make a ball rotate around a vertical axis using only a combination of horizontal axis rotations?
What is the model of "pushing" here? I would assume it means applying an impulse to instantaneously change the angular velocity, $\omega_\text{after} = \omega_\text{before} + \Delta \omega$, but then the answer is a trivial "no".
Jul
24
comment Can one make a ball rotate around a vertical axis using only a combination of horizontal axis rotations?
By the way, this is known as a kugel ball. Question: by "turn around the vertical axis" do you mean produce a net rotation or impart an angular velocity about the vertical axis?
Jun
10
awarded  Teacher
Jun
10
answered How fast do you need to travel to go 35 light-years in 2 (apparent) years?
Jun
10
comment How fast do you need to travel to go 35 light-years in 2 (apparent) years?
Actually, your first formula is backwards. The proper time experienced by an observer moving with speed $v$ for time $T$ is $t' = t\sqrt{1 - v^2/c^2}$. Otherwise, you would experience more time the faster you go, in contradiction to the twin paradox.
Sep
28
comment Physics tension question
Yes, that's correct. Another way to see this is that it takes 180 N to accelerate the 60 kg body at 3 m/s², and the only place that force can come from is the tension in the cord.
Nov
11
awarded  Supporter