8,506 reputation
11540
bio website
location United States
age
visits member for 3 years, 10 months
seen 8 hours ago

Started programming on a ZX spectrum in the 80's and have moved through Assembly, Turbo Pascal, C++, C#, Fortran. My main area of focus is engineering and scientific computing like numerical methods and 3D graphics.


Sep
4
comment Two runners on two different tracks
Are you sure it is not $x<1.35180804325785738425143629604\boldsymbol{5}$? Joking aside, usually you round numbers to a sensible value before writing it down.
Sep
4
comment Finding directions of the internal forces within a freely jointed rigid object?
The question asks for forces acting on BC at B and hence looking for $p$ and $r$, not $X$ and $Y$. So the answer is correct.
Sep
4
revised Finding directions of the internal forces within a freely jointed rigid object?
added 590 characters in body
Sep
4
comment Finding directions of the internal forces within a freely jointed rigid object?
I am looking at a more detailed answer now. I am trying to deduce if I have to use $\sin \beta = \sqrt{1-\cos^2\beta}$ or would in cancel out.
Sep
3
answered Finding directions of the internal forces within a freely jointed rigid object?
Sep
3
revised Finding directions of the internal forces within a freely jointed rigid object?
added 2 characters in body
Sep
3
comment Finding directions of the internal forces within a freely jointed rigid object?
In statics, the point at which moments are taken does not matter, but if you switch the sense of the $x$ axis for example, you have to switch the sense of what a positive moment is also.
Sep
3
comment Integrating with respect to time a double derivative $\ddot\phi + \frac bm\dot\phi = \frac{F}{mr}$
Is $F(t)$ or a constant?
Sep
3
revised Coriolis deflection:- is it 4 times if the object is thrown up, compared to a drop?
added 1 character in body
Sep
2
comment Water bottle moment of inertia
A full bottle has its center of mass near the geometric center and thus easier to spin. Half bottle, the water moves to one side and the center of mass is no longer near the pivot. Look at physics.stackexchange.com/q/80433/392 for the mathematical explanation of motion not about the center of mass.
Sep
2
comment Will I be able to push a small object in front of me in the outer space?
You have the answer already. You will move back slightly while the ball moves forward. Think conservation of linear momentum.
Sep
2
comment Would equations for a spinning top be an (x,y,z) vector
Please post your questions in Physics as you encounter them.
Sep
1
comment Would equations for a spinning top be an (x,y,z) vector
possible duplicate of Derivation of Newton-Euler equations of motion
Sep
1
comment Would equations for a spinning top be an (x,y,z) vector
See physics.stackexchange.com/a/74484/392 for how to apply the equations of motion.
Sep
1
comment Would equations for a spinning top be an (x,y,z) vector
What is your level of understanding of vector mechanics and dynamics?
Sep
1
comment Show that the profile of the hill is a cycloid
So what have you tried? Have you looked at the equations of the rock height? How about looking at how the shadow moves as a function of instantaneous dome slope (at height)?
Aug
31
comment Why is the cross product between two vectors calculated by the determinant of a matrix
What I mean is that the $[\vec{a}\times]$ matrix transforms the $\vec{b}$ vector. For example in a rotating frame $[\vec{\omega}\times] \vec{r}$ returns the rate of change of the components of a body fixed vector $\vec{r}$. The $\times$ takes a vector and turns it into an operator (like a function but in vector space).
Aug
31
comment Why is the cross product between two vectors calculated by the determinant of a matrix
I always look at the cross product as a linear operator $$ \vec{a}\times\vec{b} = \begin{pmatrix}0&-a_k&a_j\\a_k&0&-a_i\\-a_j&a_i&0\end{pmatrix}\begin{pmatrix}b_i\\b‌​_j\\b_k\end{pmatrix}$$
Aug
31
revised Particle displacement at a rarefaction or compression
added 2 characters in body
Aug
29
comment What formula connects the moment of inertia and angular velocity?
-1 because although you answered the question, you did not provide additional information that might help the OP in the future. Like the fact that angular momentum above is only valid on the center of mass. Otherwise you have to consider the parrallel axis theorem and the cross terms $ \vec{r} \times m \vec{v}$ from the motion of the center of mass.