Recent content by bokonon

Can you help me out a little bit more about how to take that integral?

1. The power into a circuit element in the product of the voltage across the element and the current through the element. Assuming a voltage v(t) = V_p cos(omega*t) across inductor L, integrate the power over one cycle and show that the net energy into the inductor is zero. V_p is the peak...

"The phase shift is either 180˚ (1/2 wavelength) or none at all. It is determined by the interface being fast to slow, or slow to fast mediums." You're speaking strictly about reflected rays, right? I'm still confused about why there are any phase shifts at all. Thanks

So you're saying that the answer to the first part of the question is that all of the different conditions for the indices of refraction make no difference, as no refracted rays experience a phase shift? I'm thinking for the reflected rays there is a phase shift when n2>n1, intuitively I'd...

1. A ray of light is incident onto the interface between material 1 and material 2. There is a figure, which is a standard figure of a ray in medium of n1 striking an interface where medium2 (with n2) meets medium1. As is typical, some of the light is reflected and some is refracted. The...

Great, thanks for your help. You haven't by any chance also been assigned 15.58, the boat problem? There's a thread called "buoyancy force on a steel boat", where I describe my work on it.

I'm having trouble with this one too. I figure, the weight of the boat is equal to the weight of the bottom plus the weight of the sides. However, one thing that is unclear is if the sides are added to the very end of the bottom, or if they are placed on top. In the later case the height of...

Oh just realized that was posted some time, probably doesn't need my services, but . . . Bluebear, I'm stuck at xmax = sqrt(4y(h-y)) I literally just substituted the answer from A into B. But I think we have to get rid of y somehow so I'm hesitant to submit this. Have you gotten it yet?

I typed in your equation for v and its correct. For my services, you think you could explain a bit how you got it?

There's no g in that equation

Grateful for your help, and the problem is clearing up in my mind. One more thing about signs though. I thought that energy values were scalars and not vectors. So signs only come into play when there is a vector in the equation? Are the only variables affecting the signs the velocity of the...

Ok, so the initial spring force doesn't matter right? And potential energy of the block, since we aren't given the height the block is above the ground, how does that get involved? I'm pretty lost . . .

"The simplest way woul dbe to define the spring extention to be 0 at the top of it's motion when the bullet hits. Then spring extention = distance moved (except for signs)" And in that case the initial elastic spring force (.5ks^2) = 0?

The problem states that d is the distance the the spring compresses when the bullet hits it, and x is what I'm unsure of, but I think it is the amount that the spring is already stretched because of mass M hanging from it.

Right, conservation of momentum sets up the equation: mVb=(m+M)Vf, where Vf is the final velocity of the block w/ embedded bullet. And for the energy conservation part, I have this: .5mVb^2 + Mgy + .5kx^2 = Mg(y+d) + .5kd^2 I'm confused about the spring. Initially it has a potential...