Recent content by bfr

When exactly are they conserved? For example, one question involved a person jumping off of a circular platform (that rotated without friction), and when the student jumped off tangentially, the platform started spinning. The question asked which of the following is conserved - angular...

Homework Statement I did a lab today where a weight was tied to a string. The string was wrapped around part of the circumference of a wheel, and then the end was taped down. So, when I let go of the wheel and the weight, the force of gravity on the weight causes the wheel to turn. I have...

Homework Statement Determine the curl on the surface of the bounded region consisting of the bottom part of the sphere with equation 625=z^2+x^2+y^2 where z<=20, in the force field F(x,y,z)=<x^2 * y,x*y^2 * z,2x> Homework Equations...

[SOLVED] Tension Question(s) I'm kind of confused about how tension works. For example, If I had two blocks that massed 5kg hanging on either side of a frictionless pulley, what would be the tension of the rope connecting them? If one of the blocks massed 2kg and the other were 5kg, what...

Er, oops :eek:. Then I guess x+2y+5z=0 would simply be the answer?

Homework Statement Suppose that f is a vector field such that curl f=(1,2,5) at every point in R^3. Find an equation of a plane through the origin with the property that \oint_{C}f dot dX = 0 for any closed curve C lying in the plane. Homework Equations...

OK, thanks. And, er, yeah, I meant from t=0 to t=2pi.

If a question says something like: "evaluate \int(x*z*y)dx - (x-y)dy + (x^3)dz from (1,0,0,) to (1,0,2pi) along the curve (x,y,z)=(cos(t),sin(t),t)" or something like that, this is just basically splitting up a line integral? In my example, it would be the same as: \intcos(t)*t*sin(t)) *...

Out of solids, liquids, and gases, which has the most potential energy? I'm pretty sure gases have the most kinetic energy, but I'm not completely sure about potential energy.Also, do exothermic reactions convert potential energy to kinetic energy, right? So then endothermic reactions covert...

Homework Statement I'm trying to find out how to use the formula t'=t*sqrt(1-v^2 / c^2) for time dilation. For example, if object A were moving .8c and object B were moving .6c, would I do .8c-.6c=.2c, and substitute that in for v in the time dilation formula to find the time object B...

OK, I didn't know we're just supposed to assume that n=1, thanks.

Homework Statement A ray of light strikes a piece of glass (n=refraction index=1.5), making an angle of 30 degrees with the surface. What angle does the refracted ray make with the surface? Homework Equations Snell's Law: n1*sin(theta1)=n2*sin(theta2) The Attempt at a Solution...

My friend calculated that the wave moved anywhere from about 30cm/s to to 130cm/s when we varied how hard we pulled on each side (he got these velocities by timing the waves). It looked kind of fast. The entire medium was relatively short (70cm maybe), though, which made it harder to time and...

A few friends and I built a wave "machine." It's made by laying out brass "rods" about a foot long next to each other about an inch or so apart on tape, and then taping the top side. When holding both sides of this "machine," when one strikes one rod at one end, it makes the rod in front of it...

Homework Statement Homework Equations wave velocity = frequency * wave length The Attempt at a Solution Well...I'm not sure. I know how you could find the distance to the person to the right using trigonometric, but I don't know how to actually answer the question...