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    Man versus Iron Weight On page 2 of the above pdf there is an example in a box with title 'Acceleration' which states that there is a difference between a man pulling on a rope with 600N force and an iron weight of 60Kg (g = 10) tied to the rope. The difference being that once the...
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    I was changing a light pendant today

    and considered doing this with just the switch turned off. After turning off the switch I checked the voltage with a meter in A/C mode. It was 140V which I thought a tad high. When I turned the switch on the reading was 230V as expected (in the UK). So I turned off the lighting circuit at the...
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    Power from F time v

    Suppose you have a frictionless and perfectly balanced conveyor belt going into space (and back). The belt is driven by a motor on earth. Suppose you want to send a person who weighs 100kg into space and you boost them onto the conveyor belt at 1m/s with the conveyor belt running at 1m/s (the...
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    Why kinetic energy is proportional to velocity squared

    Could someone please explain why kinetic energy is proportional to velocity squared and not just velocity. A propulsion system that provides a constant force would typically use energy at a constant rate in order to accelerate at a constant rate and thus rate of change of velocity would be...
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    Transmission Error Detection

    Hi, I have a small fixed size packet of information that I want to transmit and detect errors with a high degree of confidence (no correction is required). I'm guessing that a CRC is probably the way to go but don't know how to work out what form of CRC to use. I want to be able to specify a...
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    Electric Field, Mass, Length

    I believe the following are all true for an observer in a different inertial frame : An object's length is contracted in the direction of its motion An object's mass increases under motion The strength of an electron's field is reduced in the direction of motion The strength of an...
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    Charged particle in a magnetic field

    When two current carrying wires are place beside each other they are are either attracted or repelled by the magnetic fileds generated and these fields are just electrostatic forces caused by the relativistic effect. Why does a stationary charged particle not feel this force from a single...
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    Electricity & Energy

    Hi, I am trying to understand how energy propogates in an electric circuit and found this website : Assuming the site is correct, and it kinda makes sense to me, I wanted to clarify some things : Does most of the energy flow closest to the...
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    Medical Optical Illusion

    We are all familiar with the illusion of the wheels on a car on television appearing to spin backwards when the car is travelling forward, this being caused by a mismatch of the picture frequency and the wheel's rotational speed. However I have also observed this phenomenon in the real world...
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    Physics or Biology

    I don't know if this is the right place to post this question, but you're a clever lot so i'm sure you'll know the answer. We are all familiar with the illusion of the wheels on a car on television appearing to spin backwards when the car is travelling forward, this being caused by a mismatch...
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    Feynman, photons and magnetic fields

    In one of his lectures Richard Feynman describes the effect of a magnetic field on an electron. In doing this he describes the magnetic field as being made up of many photons. If a photon is an oscillating electromagnetic field how can it be just a magnetic field also ?
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    Electric Field Propagation

    Hi, I'm trying to get my head around electric field propagation in an electric circuit. If you have a battery with no circuit I imagine the electric field between the terminals would look like the magnetic field lines between the two poles of a magnet. What I can't visualize is what the field...