1. J

    Determining length of a tube with applied pressure

    Hi folks, I have a question. Imagine i'm blowing air through a duct that is capped in one side. The tube is made of plastic and has a 14mm external radius and an internal readius of 10mm. If I apply a constant pressure of 16 bar, and it takes 30 seconds for the air to come out on the...
  2. N

    Length contraction

    If we are on space ship which is travelling with the speed near c. And there is an observer on the earth who is watching the space ship. Who would experience length contraction and why? So if there is a table on the space ship. And we measure it's length when travelling with the speed near c...
  3. A

    Given tension, mass, length, find the mass

    "The string on a conical pendulum is 2m in length an has a tension on the string holding the object has a mass of 100 N. The radius of motion is 0.4 m and the period of rotation is 2 seconds. What is the mass of the object?" Does anybody have any resources to help solve this problem?
  4. N

    Basic question about primary mirror and focal length

    I have a Cassini PM-160 spherical mirror used in telescopes as the primary mirror. The mirror is concave with a radius of curvature of 2600mm and focal length of 1300mm. I am using the mirror in an imaging application. I have a very basic question. If an on object is located beyond the focal...
  5. J

    Equivalent length of helical coil

    Hello, I am trying to calculate the equivalent length of a copper winding with several mitered joint extensions on both ends in order to divide it into equally flowing sections. Through some searching online I found a site that lists Appendix A-29 from the Crane Flow of Fluids paper. I've...
  6. V

    Analytical relation for the length of the wake behind a cylinder in an external flow

    Hello all, Does somebody know if there is an analytical relation to calculate the length of the wake formed behind a cylinder in a turbulent external flow of air? There are analytical equations to calculate the pressure field and velocity (and the lift and the drag) around the surface of the...
  7. avito009

    Example of length contraction and time dilation.

    Is my interpretation correct? When you travel at 0.999 speed of light then to you what 3 seconds has passed is actually 67.2 seconds to an observer on earth if you are in a spaceship that is traveling fast. Also 1 meter to you on the spaceship would be observed as 0.45 meters on earth. This...
  8. N

    How far from focal length of a lens does the nearest infinity begin

    Q. How can we make out whether the the object is beyond C or infinity? Q. At what nearest distance does infinity start from,from the focus(focus Of any lens or mirror)? Means is there any relation between the point from where infinity starts and the focal length or curvature of any lens or...
  9. P

    The effect of focal length on collimated light output

    I was trying to get an idea of what effect if any different focal lengths for the same diameter lens had on a collimated beam? The conclusion I have come to so far is that it has no effect on the final collimated output, only the distance the light source must be from the lens in order to...
  10. V

    regarding the length contraction and time dilation in special theory of relativity

    Respected Sir, as i read in relativity, some writer use inverse Lorentz's transformations equations and some other use Lorentz's transformations for solving length contraction and time dilation expressions with any logic that which one used in which situation. clear me this. with regards vikas
  11. F

    Question about length contraction

    If someone is moving horizontally close to the speed of light his observation of the space around him looks thinner. In contrast people's observation of the object moving close to the speed of light also looks thinner, but that only applies to the space occupied by the moving object but not the...
  12. L

    Length of the pendulum which has the same period?

    can anyone show me how to get the ans ? i couldnt understand the question. your help is much appreciated!
  13. F

    How do I integrate this problem?

    Find the length of the curve given by the parameterization x(t)=t^4-2t^2+1 y(t)=t^2-1 on the interval 0≤t≤1 I'm stuck on the integrating the function after I put it in the curve length formula of sqrt((dx/dt)^2+(dy/dt)^2). Can anyone help?
  14. J

    Temperature depence of the spin flip scattering length?

    Hey Im working with Spin valves at the moment. And im wondering if magnetoresistiance can be measured at room temperature? It should be possible, if the spin flip scattering length is´nt too small. Does anyone know the temperature depence of the spin flip scattering length
  15. A

    Optics / focal length

    I am having a very hard time figuring out this problem and was hoping I could get some help. Problem: What was the focal length when the radius of curvature was 0.70m and index of refraction was 1.8? I believe the formula is the Lens markers equation 1/f=(n-1)1/R but I would need to solve...
  16. I

    Could any smart cookie help me with this optics/focal length question?

    Hey my mind is in a complete blank, been working on this for ages! Can anyone please be a kind soul and help me out? I'll send you 2 million kudos points because I'm on the verge of tears here haha!! Thank you for all your time...
  17. S

    Length Contraction problem

    A rocket ship travels to a star 100 light years away, moving at 9/10 the speed of light. a. As measured by earth clocks, how long will it take the rocket ship to reach the star? b. As measured by clocks on the rocket ship, how long will it take the rocket ship to reach the star? What principle...
  18. B

    How do I do this with no length of the bridge.

    A hiker who weights 985 N is strolling thru the woods and crosses a small horizontal bridge. The bridge is uniform, weights 3610N and rests on two concrete supports, one at each end. He stops 1/5th of the way along the bridge. What is the magnitude of the force that a concrete support exerts on...
  19. Y

    Lever Arm Length Calculation

    Hello all, My question is this, say you have a 1 metre rod. One end is it's axis of rotation and on the other end you have a weight suspended by a 1 metre piece of string. The rod is parallel to the earth so the weight is hanging perpendicular to the rod. I'm assuming (maybe incorrectly) that...
  20. M


    The second harmonic frequency on a stretched wire, with a tension of 50 N and a mass per unit length density of 0.025 kg m-1, is measured to be 200 Hz. What is the length of the wire? ________ Can someone give any tips?