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  1. E

    'normal' set paradox

    maybe xzibit can help.
  2. E

    Collision Problem - A gain of kinetic energy?

    well, we seem to have an impossible situation here. and in fact we do. if you look at the change in KE of B, it is bigger than the whole of A's KE coming in. this is impossible. these numbers do not correspond to a possible physical situation.
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    Is there a physical reason why conservation of momentum HAS to happen?

    according to the internet, chuck norris seems to have something to do with it.
  4. E

    Collision Problem - A gain of kinetic energy?

    can you show us the work you did.
  5. E

    How to graph magnetic field between two wires?

    hmm, that doesn't look right. one thing is my fault, you need to change your units from mT to microT. but the graph itself looks wrong too. it should be symmetric and it should have a minimum at the center. make sure you are adding the fields from the two wires together.
  6. E

    How to graph magnetic field between two wires?

    sorry, hard to tell, so i just guess. anyway, we are on the right track, have you calculated the field anywhere else?
  7. E

    How to graph magnetic field between two wires?

    ideas, he quoted all the information needed in the above post. any perpendicular line between infinite wires will result in the same graph.
  8. E

    Egg drop project

    get 10,000 straws and 100m of tape and then start building and dropping. use your intuition to get started, but test, test some more, and then do some more tests; you get the idea :smile:.
  9. E

    How to graph magnetic field between two wires?

    yes, you have the idea, now you just need to calculate the field at a few more points and get the shape of the graph. you should try to take advantage of the symmetry of the situation. notice the field in the middle is 45 microtesla, so you need to adjust your scale. oops, i just noticed i...
  10. E

    How to graph magnetic field between two wires?

    oh, ok, then we can solve the problem. do you know how to calculate the magnetic field due to a current carrying wire?
  11. E

    How to graph magnetic field between two wires?

    it seems like we need to know if the currents are in the same direction or in opposite directions. does the problem say anything like that?
  12. E

    How to graph magnetic field between two wires?

    ok, that is good. that is all you can do until you figure out the currents in the wires. do you know how to do that?
  13. E

    How to graph magnetic field between two wires?

    no, all of our action will take place between the wires. you need to make the position of wire 1 = 0cm, and the position of wire 2 = 6cm, and then fill in the rest. the field we are given is for the point located 2cm from wire one, so that is where we plot the value 8.
  14. E

    How to graph magnetic field between two wires?

    ok, that should work, though you may need to consider negative B values. Now, we need to partition our axes and give them some units. we can use the one data point that we know already, (2 , 8x10^-6), to help us determine the scale we should use for each axis. the x-axis is easy, just put a...
  15. E

    Physics Project Help

    if you are thinking about the efficiency of the machine, you don't really want to think in terms of initial vs final energy, but rather energy in and energy out. what do you have to put into the thing, this is basically the cost of lifting the bricks, vs the desired output, which is the KE of...
  16. E

    How to graph magnetic field between two wires?

    the value of B and r that are given will be one point on the plot.
  17. E

    How to graph magnetic field between two wires?

    were you able to calculate the magnetic field at the point indicated in the question?
  18. E

    Manipulate the equation

    i agree with borek, getting them to do the algebra sort of kills two birds with one stone. and it is usually the more efficient way to go (but not always). cheers
  19. E

    Sound wave and intensity

    that looks correct. it seems that the problem is one of mixing up units. the correct solution you have may be in units of nanowatts per meter squared.
  20. E

    Sound wave and intensity

    can you show how you arrived at your answer?
  21. E

    Velocity Ratio of a 3rd Class Lever

    oops, now that i read the problem more carefully, i see that the MA (and so VR also) is 1/6. i read it as saying the load was 5m from the fulcrum, but it is 5m from the effort, so 6m from the fulcrum. ok, then the load and effort force make sense. now, as for the work, that's easy, energy is...
  22. E

    Velocity Ratio of a 3rd Class Lever

    i typically leave ratios in rational form, but that is aesthetics more than anything. and yes, ratios are dimensionless.
  23. E

    Velocity Ratio of a 3rd Class Lever

    you have interpreted correctly :smile: . though i feel the need to say that the distances traveled will not be 1m and 5m, but due to similar triangles, the ratio will be 1/5, and that is all we care about. cheers
  24. E

    Velocity Ratio of a 3rd Class Lever

    so, for velocity, we only need to worry about how far each end of the lever moves when we perform our task, and how long it takes to move that distance. we can ignore all the real physics stuff like force and energy for now. so picture it in your head, the long end of the lever is pulled down...
  25. E

    Velocity Ratio of a 3rd Class Lever

    why do you think it should be 1/6? you need to just think about the definition of velocity. velocity is just how far the thing goes divided by how long it took to get there (well, that is average velocity, but that's all we need here). you can use trig to solve the problem, but that is the...
  26. E

    Power series convergence

    hi, i have never seen a series like that, very interesting. i can't think of any way to call that a convergent series with that rouge term in there, not even at the center. your analysis of the radius of convergence is correct for the remaining terms. cheers
  27. E

    Angular acceleration of a cylinder?

    if the cylinder is rolling without slipping, then the angular acceleration is equal to the linear acceleration divided by the radius of the cylinder. cheers
  28. E

    Wave speed

    hi, so, we have two waves moving from point A to point B, so they go the same distance, lets call that d. but, they are going at different speeds, so they take different times. we don't know those times, but we know the difference between them, so would could say that t_{fast}=t_{slow}-120...
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