There has been some heated debate as to whether the laws of physics allow for traversable wormholes. Some physicists claim we require exotic matter to construct wormholes, but then others counter the Casimir effect with ordinary matter is sufficient. But these same physicists seldom come up with an explicit solution or state of ordinary matter keeping the throat of a wormhole open via the Casimir effect. Yet others claim with extra dimensions, a Gauss-Bonnet interaction is sufficient to keep the wormhole throat open, but opposing physicists claim such a term can't arise from string theory.

So, my question is, do traversable wormholes exist as solutions to string theory?

Am I correct it remembering that unless a pulsars beams plane faces earth we can not detect them. And that similarly inbetween the pulses we can't see them either?

If so how does this differ from dark matter? Isn't it possible that there are a lot more pulsars that we just can't see them because they are pointing the wrong way.

I'm trying to solve a problem where I have an object resting on an inclined plane, with the angle of the plan being alpha, and the weight being w. I'm having trouble figuring out how I can calculate the component of the weight parallel to the plane. I also want to find out the weight component perpendicular to the plane.

I don't want an outright answer, more of an explanation to help me understand. Thanks!

Three charged marbles are glued to a nonconducting surface and are placed in the diagram as shown. The charges of each marble are q₁ = 5.95

A dipole lies on the y axis and consists of an electron at y1 = 0.50nm and a proton at y2 = -0.50nm .

Part A

Find the electric field midway between the two charges.

Express your answer using two significant figures. Enter your answers numerically separated by a comma.

SubmitMy AnswersGive Up

Part B

Find the electric field at the point x = -1.5nm , y = 0.

Express your answer using two significant figures. Enter your answers numerically separated by a comma.

SubmitMy AnswersGive Up

Part C

Find the electric field at the point x = -26nm , y = 0.

Express your answer using two significant figures. Enter your answers numerically separated by a comma.

Submit

(Go go gadget problem solver!) Joe, Bill, and Fred are playing a game with marbles at the top of an uncarpeted (wooden) staircase. They decide to try to roll their marbles off the top step and see how many steps the marble will skip before hitting. The faster they roll the marbles, the farther down the staircase the marble will go before hitting a step. Suppose one of these marbles leaves the floor at the top of the staircase at 2.54m/s. Each stair is 20.0cm tall and 20.0cm deep. Which stair will the marble hit first? Clearly label your answer on a picture/sketch. [Hint, you don

A catapult launches a test rocket vertically upward from a well, giving the rocket an initial speed of 79.8 m/s at ground level. The engines then fire, and the rocket accelerates upward at 4.20 m/s2 until it reaches an altitude of 980 m. At that point its engines fail, and the rocket goes into free fall, with an acceleration of ?9.80 m/s2. (You will need to consider the motion while the engine is operating and the free-fall motion separately.)

(a) For what time interval is the rocket in motion above the ground? s

(b) What is its maximum altitude? km

(c) What is its velocity just before it hits the ground? m/s

An ideal gas with ?=1.4 occupies 3.0L at 300 K and 100kPapressure and is compressed adiabatically until its volume is 2.0 L. It's then cooled at constant pressure until it reaches 300 K, then allowed to expand isothermally back to state A.

Part A

Find the net work done on the gas.

Express your answer using two significant figures.

Part B

Find the minimum volume reached.

Express your answer using two significant figures.

A jet with mass m = 10⁵ kg jet accelerates down the runway for takeoff at 1.8 m/s².

1) What is the net horizontal force on the airplane as it accelerates for takeoff?

2) What is the net vertical force on the airplane as it accelerates for takeoff?

3) Once off the ground, the plane climbs upward for 20 seconds. During this time, the vertical speed increases from zero to 29 m/s, while the horizontal speed increases from 80 m/s to 92 m/s.

4)What is the net vertical force on the airplane as it climbs upward?

5) After reaching cruising altitude, the plane levels off, keeping the horizontal speed constant, but smoothly reducing the vertical speed to zero, in 16 seconds.

What is the net horizontal force on the airplane as it levels off?

6)What is the net vertical force on the airplane as it levels off?

A proposed space station consists of a circular tube that will rotate about its center (like a tubular bicycle tire) as shown in the figure(Figure 1) . The circle formed by the tube has a diameter of about 1.1 km. What must be the rotation speed (revolutions per day) if an effect equal to gravity at the surface of the Earth (say 0.90 g) is to be felt?

An alpha particle with kinetic energy 15.0MeV makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude L=p0b, where p0 is the magnitude of the initial momentum of the alpha particle and b=1.30

3.

Two 2.20-?C point charges are located on the x axis. One is at x = 1.57 m, and the other at x = -1.57 m. Determine the magnitude of the electric field on the y axis at y = 0.530 m. Answer in units of N/C.

4.Three identical point charges of charge q = 7.3 ?C are placed at the vertices (corners) of an equilateral triangle. If the side of triangle is a = 5.2m, what is the magnitude, in N/C, of the electric field at the point P in one of the sides of the triangle midway between two of the charges?

5.Four charges are placed at the corners of a square. If q₁ = 44.0 x 10^-9 C, q₂ = -24.0 x 10^-9 C, q₃ = 26.0 x 10^-9 C, q₄ = -46.0 x 10^-9 C and the side of the square is a = 0.32 m. What would be the magnitude of the electrical field in the middle of the square? Answer in units of N/C.

Two in-phase loudspeakers are located at (x,y)coordinates (?3.0m,+2.0m) and (?3.0m,?2.0m). They emit identical sound waves with a 2.0 m wavelength and amplitude a.

Determine the amplitude of the sound at the five positions on the y-axis (x=0)

a)with y=0.5m

b)with y=1.0m

c)with y=1.5m

d)with y=2.0m

The usual way to model a vibrating membrane is by using the wave equation. Is it possible to do that from "within"? Probably the answer is yes, but where can I see it done explicitly. What I mean is can we model the membrane as a two dimensional Riemannian manifold without any specific embedding in R3 plus equations involving the metric (or form, tensors etc.) such that at any time it is isometric to the surface given by the graph of the function satisfying the wave equation at that time. Higher dimensional generalizations are also interesting.   

I'm trying to explain in simple terms what the weak interaction does, but I'm having trouble since it doesn't resemble other forces he's familiar with and I haven't been able to come up (or find on the web) with a good, simple visualization for it.