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  1. M

    Electric field inside hydrogen atom.

    The term "A" is probably going to be composed of two parts that add together. Try thinking about how to use a combination of step functions (or delta functions) to represent the electron and proton. Arfken has a little bit of material on this. If you have not had delta or step functions, I will...
  2. M

    Uncertainty principle

    delta_r is your delta_x. The speed of the electron is not relativistic. (at least I don't remember it to be) Use the momentum to get your kinetic energy. Then convert units.
  3. M

    Battery provides a potential difference problem

    Normally what you would do is integrate the current flowing from the battery to the capacitor. This means taking into account the resistance of the wires and anything in between the capacitor and battery. But if you haven't had this, LET CHEAT! We really don't need to know all the minutia...
  4. M

    Battery provides a potential difference problem

    good job. Don't forget your units. Now remember that the charge entering the one side of the capacitor has to equal that returning to the battery from the other side. Have you learned about time decay of capacitors yet?
  5. M

    Battery provides a potential difference problem

    Can't see the image. But let's start with how much charge IS in the capacitor? Write out the equation, and tell me. I will be online for another 10 minutes. We can solve this in 5 minutes.
  6. M

    A thought regarding angular acceleration, gravity, and weight.

    FYI Don't know how much vector formalism you post-ers are into but writing down "centrifugal force" as F = -m*OMEGA x (OMEGA x R) gives you the forces of interest. Here OMEGA is you angular velocity vector, and R is the radial vector. Do the calc (pad and paper) and you will get the nice...
  7. M

    A thought regarding angular acceleration, gravity, and weight.

    A very good first go. The centrifugal force in Ohio points "south." This is a question we normally give our undergrads in intro physics. Usually our question also asks "Why are space shuttles and rockets launched close to the equator?" If you plot out the centrifugal force felt by an object from...
  8. M

    Diameter and resistance

    Good for you!
  9. M

    Diameter and resistance

    First solve for the variable you are looking for and put it on one side. Keep your knowns on the other side. Remember that A stands for area, and area is related to wire diameter. I am online for a bit, so give it a go. DON'T FORGET YOU UNITS!
  10. M

    Force and angle

    Newton V, good basic question. As you may have learned from your intro class, forces are represented by vectors. This is because they have magnitude (strength) and direction. What you should do 1) draw a picture of the problem. 2) Draw the force diagram, 3) break the forces into components, in...
  11. M

    Maximum attainable coefficient of static friction

    Fair enough. Let's assume that the front tires "barely" leave the ground. This implies the rear tires DO NOT slip. Now since you know that the vehicle starts from rest, (1) what does the position equation look like? (2) From a term in this equation what term says anything about...force?
  12. M

    Maximum attainable coefficient of static friction

    The knowledge that the front tires are lifted indicates torque which is directly related to the static friction acting on the tires. If the figure tells you the angle of lift, what missing information can you compute to determine average acceleration?
  13. M

    At what distance can your eye no longer resolve two headlights?

    Your eye not diffraction limited of course. Usually problems do not hand you extra information in first/second year physics. What happens to light when it enters a lens? (Hint: The equation you are using works well for mirrors telescopes.)
  14. M

    Physics question

    GOOD! Let's tackle question 1). How much energy is needed to get to maximum altitude? (Hint: use the potential energy equation.)
  15. M

    Physics question

    GOOD! Let's tackle question 1). How much energy is needed to get to maximum altitude? (Hint: use the potential energy equation.)
  16. M

    Physics question

    For 1) what equations specifically do you think are pertinent? Write post what you have. For 2) Again write down the pertinent equations. Also draw a diagram here relating position and time. Helpers may not be able to see your picture but you may see what is happening more easily.
  17. M

    Logical Error of Cavendish Experiment

    1) GR was never "taboo." Just like any other theory (or model) it must be tested. Otherwise it is as good as math homework. 2) I already made a note as to Cavendish's intent. The by-product was the constant G. Dozens and dozens of experiments measuring G have been conducted by national...
  18. M

    Speeds greater than the speed of light

    Alll right, I sent e-mails to the previous gent/lady "azzkika". First, let's use what we know about the physical universe. 1) No signal can be sent at any rate exceeding that of light traversing a vacuum. 2) As you build "speed" (I hate that term), MASS is NOT generated. 3) Gravitational field...
  19. M

    Logical Error of Cavendish Experiment

    I think we should stop the thread here. The comment I made started with a capital "IF." This implies that you would go an compute the force roll off using 1/r^2 + beta/r^3 + gamma/r^4 etc.... (It's easy with pad and pen. Start with the taking derivatives.) Such deviation would be measurable over...
  20. M

    Logical Error of Cavendish Experiment

    Let's take Cavendish's bent on things. He wanted NOT to determine G, rather he wanted an estimate on the mass of the Earth. If you were in Cavendish's time, then you may not know Gauss's theorems yet (since Gauss came later). What you could do, is assume that the Earth is a uniform sphere. Since...
  21. M

    Speeds greater than the speed of light

    I think this thread is done. In nature, no phenomena has been observed to actually propagate faster then EM waves. Special relativity/general relativity, and the post-parameterized Newtonian models model near light speed behaviors quite well. Until superluminal phenomena are observed, this is...
  22. M

    Logical Error of Cavendish Experiment

    I am not sure where you are going with this. Is this a homework assignment?
  23. M

    What is the speed with kinetic energy

    Use your answer, plug it back into the KE equation, and tell us what you get. You might find a 10 percent error.
  24. M

    Dropped Tennis Ball

    For part a) what is the easiest way is energy relations. You got the equations on this part. Double check your numbers, though. I haven't a calculator, but it's a good idea. For part b), there is a better relation. Ask yourself what the center of mass is doing on impact. And then think about...
  25. M

    What is the speed with kinetic energy

    Agreed, check your numbers.
  26. M

    Basic Gauss's Law problem

    The continues from my previous post, I can't type as fast as you!!!!!!!!! r > r_b Left hand side = E * (4 * pi * r^2) Right hand side = (4/3) * pi * r^2 * rho / epsilon Solve for E E = (r^3 * rho) / (3 * epsilon * r^2) = (r * rho) / (3 * epsilon). You could have gotten here if you used...
  27. M

    Basic Gauss's Law problem

    Ok, I did the math on paper instead of in my head. Here is the answer. Got a pen and paper? Nope that pen is dry. Try another one. Ahh one that works. Left hand side = E * (area of a sphere ENCLOSING THE CHARGE) = E * (4*pi*r^2) Right hand side = Q/epsilon...
  28. M

    Basic Gauss's Law problem

    This looks right on first glance. The integral on the left should yield E*(area enclosed by a sphere) = E*(4*pi*r_b^2) . The right hand side is simply, the charge density times the volume of the arbitrary sphere whose r < r_b. Q = (4/3 pi r^3) * rho. Therefore the resulting ratio should go as...
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