Energy at tree-collision
Suppose one was on a collision course, speeding towards a tree on a bicycle. Expectedly, one would suffer a horrendous crash; the rigid tree would remain static whereas the rider would likely sustain...
View ArticleSpatial frequency of pixels in an FFT transformed image
This question is about converting from spatial to frequency domains when performing an FFT on 2D image data. I suspect my problem has a painfully obvious solution that I'm just not seeing. If I have...
View ArticleLenz's law - magnetic fields and Currents
Hey Pf.. I am trying to understand Lenz's law, but somehow it doesn't make sense. In my book there is some checkpoints execise to test wheather you've understood what you read about, one those...
View ArticleMisconception of Newton's laws?
A bird flies by pushing downwards the air below its wings with a force. According to Newton's third law, the air pushes the wings upwards. As a result, the bird is lifted. Also consider the case of a...
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Torque Sum with applied torque off axis
I think I'm missing something really simple here due to being out of school for a while: In a free body diagram, if I am trying to take the sum of torques about point 1, how should I deal with an...
View ArticlePotential difference of an inductor equal to minus the induced emf?
Hi, Two questions I'm finding it hard to get my head around with inductors... Say we have an increasing current, this is going to cause an increase in flux in one direction, which will induce an emf to...
View ArticleWhy is the gas energy in a g-field 5/2KNkT ?
I am messing around with classical gasses using a demon algorithm, trying to reproduce the behavior of ideal gasses in various situations. Exitingly, this is working very well. Here are my findings so...
View ArticleDispersion Relation: Beads and String
When making the transition from the dispersion relation for a beaded string to the relation for a continuous string, I'm confused about the following issue. Take a to be the spacing between beads, m...
View ArticleWhat affects the light intensity and light output geometry?
These are some of the factors I brainstormed that goes into the functionality of a spotlight: 1) Light output of the light source (measured in luminous flux, if I recall correctly) 2) The reflective...
View ArticleWater in rotating cylinder
A question I was doing asked to find the equation describing the surface of water placed in a cylinder rotating about its central axis. The question asserts that in the rotating frame, the water is at...
View ArticleRocket Burning fuel causing change in mass
I made up a scenario: Let's say I have a rocket at rest in space. The rocket initially weighs 100 kg, 50 kg of which is fuel. If the fuel burns at a constant rate of 1 kg/s and produces a thrust of 100...
View ArticleCoupled Equations Motion/Rotation
I'm looking for the set of equations that describe an untethered rigid body about a body fixed axis in relation to a reference axis (ECI or etc.). I'm not sure what they are called. I was trying to use...
View Articleinternal resistance understanding
Hello, I'm having difficulty trying to understand internal resistance of any component. I don't understand how exactly the internal resistance affects the current and what exactly is the terminal pd?...
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Where is the electron in this picture.
The path of an electron in a magnetron is shown along with the electric field, see below. Assume the electric field shown is maximum at time t. Without calculation can you argue and approximate where...
View ArticleAcceleration and Light
Hello all , When a photon gets closer and closer to black hole , gravity affects photon and changes direction of photon's moving . Is that mean photon gets acceleration near gravitational field ? Thanks.
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Car negotiating a bend - Forces
- Sorry posted in the wrong section please delete - Hi, I am confused a little bit with the forces acting on a vehicle when it's negotiating a bend, at constant speed. Please click the link to see my...
View ArticleEscape Velocity at an angle
The escape velocity of an object on the surface of the Earth is the minimum speed required for it to "break free" from the Earth's gravitational field without requiring further propulsion. Its value is...
View ArticleUsing magnetic energy and causing degradation of the field
Hi guys! I was wondering something about magnetic energy and well, I stumbled on to this. If there was a way to use a magnetic field's energy without influencing the actual magnet, would the...
View ArticleDeriving V(t) = L (di/dt)
Voltage across an inductor at any moment in time can be calculated as the inductance multiplied by the rate of change of current. How is this equation derived? I'm pretty sure it comes from Faraday law...
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Rate of evaporation and steam tables
Looking at the steam table below, if I understand things correctly, it will take 419kJ to bring a kg of water to the boil at 100°C and a further 2257kJ to turn all of that boiling water into steam. I...
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