9,992 reputation
21744
bio website
location United States
age
visits member for 4 years, 5 months
seen 43 mins 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.


1d
comment Does it take more energy to open a door when applying force close to the hinge?
The force needed to accelerate the center of mass.
1d
comment Can someone explain this solution for the motion of a falling chain?
2) Tension affects the center of mass of the falling size, but also the center of mass of the stationary side (since more and more of the chain becomes stationary). The net result is zero.
1d
comment Can someone explain this solution for the motion of a falling chain?
1) If the chain is falling on the right side, after it whips it is going to be rising on the left side. That horizontal motion is going to carry kinetic energy but only for a negligible fraction of time. After that is going to loose all horizontal motion. So when looking at before and after only the vertical motion accounts for change in kinetic energy.
1d
comment One force applied to one point of a rigid body: centre of mass and torque
See Do objects rotate around the torque vector or its center?
1d
comment One force applied to one point of a rigid body: centre of mass and torque
See Derivation of Newton-Euler equations of motion
1d
comment One force applied to one point of a rigid body: centre of mass and torque
The correct equation is $$\vec{\tau} = \frac{{\rm d}I \vec{\omega}}{{\rm d}t} = I \vec{\alpha} + \vec{\omega} \times I \vec{\omega} $$
1d
revised One force applied to one point of a rigid body: centre of mass and torque
math formatting
1d
comment Schrödinger Equation
Are you trying to establish a physical interpretation of a wavefunction on a human scale?
1d
answered Can someone explain this solution for the motion of a falling chain?
1d
comment How to calculate the normal force exerted by a fulcrum off-center?
There must be another support, or the rod would move (tilt). The answer differs depending on the situation.
2d
comment Does it take more energy to open a door when applying force close to the hinge?
What is missing here is the part of the applied torque that goes into the inertial forces.
2d
comment Does it take more energy to open a door when applying force close to the hinge?
Theoretically without springs and without friction it takes (almost) zero energy to open the door. Maybe the question needs to rephrased as the energy required to reach a certain rotational speed $\Omega$.
2d
comment if you have an object on an inclined slope, by applying a horizontal force would you be able to lift the object from the slope?
This question lacks a free body diagram illustrating your question.
Apr
15
comment Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
For each collision. Apply it three times (hence the three equations) to get the three unknown impulses. This is nothing new here. Read cs.cmu.edu/~baraff/sigcourse/notesd2.pdf on how to implement algos for multiple collisions.
Apr
15
comment Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
They are not energy equations. They represent the before and after of relative velocity $$v_{final} = -\epsilon v_{initial}$$ See scienceworld.wolfram.com/physics/CoefficientofRestitution.html
Apr
14
comment Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
I had the same concerns but the OP stated in comments that this is really more like a game and not a simulation. The positions are quantized (snapped) to a hex grid so the collision will occur at the same time.
Apr
14
comment Tensions in a rope
Tension is defined as the force you need to apply to a part of the rope so it does not move.
Apr
14
comment Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
And you may wish to award whatever answer you want. Just upvote the ones that are useful to you.
Apr
14
comment Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
For 3D use physics.stackexchange.com/a/92132/392
Apr
14
revised Is this solveable? Simultaneous elastic collision of 4 objects in XY plane
added 193 characters in body