1. E

    A mathematical model for natural cooling of a cup of tea/coffee/ etc.

    hello I have some problem modeling an approximate model of natural cooling of a cup of tea/coffee left in a closed and controlled room. I attached a detailed PDF document (called 01.10.19) that describes all the details regarding the questions I am going to ask below. 1st questions...
  2. T

    Damped Oscillations and Natural Frequency

    Hello everyone, recently I've learnt that by damping, it is possible to reduce the natural frequency of an object. Therefore, can anyone kindly explain how this works? Why would damping reduce the natural frequency of an object? Thank you very much! :)
  3. A

    Natural convection: turbulent or laminar?

    Hello everyone, I am modelling an inclined rectangular cavity and got confused with Grashof and Rayleigh number. I've reviewed many research papers - some researchers use Rayleigh, some Grashof number to determine the type of flow. This is probably very simple but I can't find where my...
  4. C

    Determine the natural frequency 2

    The question is: Determine the natural frequency of the rotor shown below given the following data: Moment of inertia of rotor Jr=0.6 kgm^2 Diameter of shaft d=38.0mm Length of shaft L=189.0 mm Material of shaft Steel Modulus of Rigidity 82 GPa My solution is...
  5. C

    Determine the natural frequency

    Determine the natural frequency in Hz of the system sketched below given the following values: Mass m=10kg Spring stiffness k=18kN/m Length a=114mm Length b=120mm I know that ω=(k/m)^0.5 So probably I need to calculate m. Should I write m=10*9.81*(0.114+0.12)?
  6. H

    Resonance,Resonance frequency,natural frequency?

    Say here is an empty bottle of coke., and you know for sure that the bottle resonates most at 320hz. when the bottle resonates, the bottle will vibrate. the question is, 1.if the bottle also resoates at 318hz( bu not most), will the bottle vibrate 318 times per second or 320times per...
  7. R

    Water natural convection

    Hello, I have an interesting question about water natural convection without an external heat source. Say we have a high tower filled with water. The tower walls don’t allow any heat to escape or enter the system. There is a constant gravitational force present in a system (g-force). At the...
  8. W

    Strain and natural length

    In a problem, it asked if strain depends on unstretched length of a uniform wire when stretched. The answer is no. But the equation strain=\frac{e}{L} e is the extension and L is the natural length Why isn't stress depends on natural length? Does it mean that strain is a constant...