Recent content by MarkH748

  1. M

    Undergrad Torque required to reduce the speed of a rotor?

    Hi, I'm currently trying to find out how to calculate the torque required to slow a rotor down from a high rotational speed to a low rotational speed. I know the inertia of the rotor, the 2 rotational speeds and the time it needs to take to slow the rotor down. Is there a method or formula...
  2. M

    Undergrad Finding the safe rotational speed of a carousel?

    Hi, I'm currently working on a project for a braking system of a carousel. Basically in order to start designing the brake I need to know what the maximum rotational speed of the carousel should be. The max diameter of the surface will be 2 meters and the maximum speed at the periphery should...
    • MarkH748
    • Thread
    • Rotational rotational speed Speed
    • Replies: 1
    • Forum: Mechanics
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    Which of these spring systems is equivalent?

    Hi guys. I looking at a vibrations problem with 2 springs in it (System A). I need to find an overall value for the stiffness K to find the natural frequency of the system. I know that normally when 2 springs are in series I should get the sum of (I/Ki)^-1 which would give me an equivilant...
  4. M

    Is the overall heat transfer coefficient constant for a certain heat exchanger?

    Hi guys. Without going into too much detail. Basically I have a counter-flow heat exchanger problem where I need to find one of the outlets temps only given the inlet temps of each fluid. I have no idea how to do it though as I'm not given a value for over heat transfer coefficient (U) or...
  5. M

    How long does it take a Capacitor to charge to 80% of its final value?

    Ah, I put V equal to 2 volts by accident. Putting it equal to 8 gives me t = 0.9047 s. Thanks for your help.
  6. M

    How long does it take a Capacitor to charge to 80% of its final value?

    I think I understand now. When t -> infinity, Vc = 10 V (this is correct?). So I need to find a value for t for when Vc is 8 volts using one of the methods you mentioned? edit: this gives me t = 3.6188.
  7. M

    How long does it take a Capacitor to charge to 80% of its final value?

    I'm still unsure. Do I say @ t = infinity, Vc = 10 - 700I ? I don't have a vlue for I though. Do I need one? I'd also be interested to know how you estimated 0.95s. Could I write in an exam, "By observation, t = 0.95s" ? or would that be meaningless?
  8. M

    How long does it take a Capacitor to charge to 80% of its final value?

    Homework Statement I have a a circuit with an inductor, a resistor and a capacitor in series. I have analyzed the circuit and gotten an equation for the voltage across the capacitor to be. Homework Equations Vc(t) = 10 + (20/3)e^-5t - (50/3)e^-2t The Attempt at a Solution I...