Recent content by bobbles22

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    Work Function Questions - Help Bob Find the Answer

    Hi all, I'm trying to understand work functions and am working through a paper but keep coming up with the wrong answer. Can anyone point out where I'm going wrong please... Wavelength of light incident on surface = 560 nm Max speed of ejected electrons = 1.67 x 105 ms-1 1 eV = 1.602 x...
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    Question Regarding Capacitance And Inductance

    Its a simple circuit with just a capacitor and a solenoid, nothing else
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    Question Regarding Capacitance And Inductance

    Hi there, I'm doing a home study course including a section on dynamic fields and waves. I am trying to understand how to find capacitance using initial charge, inductance and energy. From a previous section, I know I can find the maximum current using Um=1/2 LI2 However, I can't see...
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    Calculating Distances in Special Relativity - Bob's Question

    Hi there, I think I understand how, using Lorentz transformations, I can find relative speeds of objects within different frames of reference. However, I'm struggling to transfer that understanding to distance. I'm sure that the distance as measured by observers within two different...
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    Pressure At Surface And Scale Height

    Please can someone tell me if my thinking here is right... I've got a planet with an atmospheric pressure at 6km of 0.5 P0 and at 8km of 0.4 P0 (P0 = pressure at the surface). I want to work out the scale height of the atmosphere. Given scale height = λ and for height above surface...
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    Most Probable Speed - Atoms From An Oven

    Hi there, I'm looking to find the most probable speed of atoms ejected from an oven. Temp (T) is 900°C (so 1173.15K). The material is aluminium with molar mass 0.027kg mol-1 I've got the formula vmp=√(2kT/m) I'm fine with everything above, but I'm not sure what value to use as...
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    Help With Conservation Of Energy Concept

    Hi guys, Can someone help explain something to me. In a situation of an asteroid heading straight towards the Earth, I'm trying to understand where the energy comes and goes (using just gravitational potential energy and kinetic energy). Consider the energy of the asteriod some distance...
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    Initial-Value Problem Integration Question

    Hi there, I'm doing a maths uni pre course with some questions on differentiation and integration. I'm looking for a few pointers on how to proceed. I need to solve: dy/dx=(cos(3x))/(2-sin(3x)) when y=2 and x=0 Can anyone help with how I'm meant to approach this and how I go about...
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    Tension in a Wire: Calculating Maximum Load Capacity

    Hi Guys, Firstly, I'm not a school student, I work for a cable company. This is just a question I was wanting some verification on regarding a situation for a quote we have in. We have a client wanting 50m of a cable to hang clothes on in a warehouse. The breaking load of the cable (if...
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    How Do You Calculate the Force to Slow a Spinning Disc to a Stop?

    Yes, the clay was added as an earlier part of the question, hence I originally only had the moment of inertia of the disc (0.0004) and then changed it for the moment of inertia of both the disc and clay (0.004 + 0.005 x 0.0016 where the distance of the clay from the centre is 4cm, and its mass...
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    How Do You Calculate the Force to Slow a Spinning Disc to a Stop?

    Opps. I forgot to add the lump of 5g of putty 4cm from the centre of the disc. This makes the total moment of inertia (0.004+0.005x0.042. Therefore 0.06f=0.000408x20pi so f=0.427N But, thank you if you think that is right :wink:
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    How Do You Calculate the Force to Slow a Spinning Disc to a Stop?

    Homework Statement I need a quick sanity check here please. (Sorry, my alphas keep coming out as power signs, they're not!). To find the force to slow a spinning disc with known moment of inertia (0.0004kgm2) and known angular velocity (120pi rad/s) to a stop in 6s. Here, the...
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    Calculating Time and Speed From Verticle Height and Acceleration Due to Gravity

    I have a very simple question. If I know that a projectile reaches a maximum height of 15m from its launch point, how to I work out the original speed and the time of flight given the only force is the downward acceleeration due to gravity. I'm sure its very easy, but I can';t remmeber the...
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    Tension of wire between posts with weight added to the wire

    Thanks for everyones help with this. So you are aware, the figures I have put in are 7000mm initial length, 8mm extension (rounded up from 7.96mm) using Diameter 4mm (therefore radius 2 of course), Young's Modulus is 70,000N/mm2. Using this 8mm extension, I found the angle to be 2.74 degrees...
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    Tension of wire between posts with weight added to the wire

    Thank you for that NVN. Could you explain how you reached that answer. I got approx 24,000N. I worked on the basis that I knew the wire would stretch about 7mm, worked out the angle of the bend from horizontal, then took the 1000N acting down and worked out the horizontal compoment of it. Have...
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