swansont

I don't think "all virtual particles" is right - lots of virtual particles are not ones with zero rest mass. Particles with zero rest mass travel at c because that's the solution to the equations. Particles with rest mass travelling at either v<c or v>c are also solutions to the equations, but they are different solutions from each other. So tachyons, if they exist, can never travel slower than c. What do you mean by 'time travelling at the speed of light'?

A force that is at some angle is the same as the sum of two forces, one horizontal and the other vertical, and whose magnitude is given by the Pythagorean theorem if you were to draw the right triangle with the three vectors. The horizontal and vertical parts are the components. How big any given component is depends on the angle - you can use trig to figure that out. In your example there are other forces present that are not named. Gravity, for instance, exerts a force downward. The upward component of the force the rope exerts acts against gravity, and makes no contribution to the forward motion. That component would be given by the sine of the angle (400N * sin30). The component of the forward force is given by the cosine (400N * cos30) (using the angle in your drawing) (400*sin30)2+(400*cos30)2=4002 so you can see the component forces add (as vectors) to be the total force of 400N

The cosine tells you the component of the force doing the work. The perpendicular component doesn't contribute.

The dot product, that gives you the cosine, tells you what the projection of the vectors are onto each other. i.e. how much of the force is in the same direction as the displacement. A force that is perpendicular to the displacement can't add or remove energy, thus it does no work. A force that is in the exact same direction as the displacement does the maximum work possible. The cosine, in essence, tells you how efficiently you are doing the work with that force.

Also keep in mind that the division between chemistry and physics was originally defined a long time ago. With more recent discoveries, there is overlap where there didn't used to be. Chemistry used to be about what happened when you mixed a bunch of chemicals together. Now e.g. with QM, the theory describes molecular bonds, so both physicists and chemists are going to study it. Just like you have biochemistry and biophysics, there's physical chemistry and nuclear chemistry and chemical physics.

You need to break the forces down into their x and y components. Only the net force in the x direction (horizontal) does any work for displacement in that direction. Any components in the y direction make no contribution.

The net force is always in the direction of the acceleration, but this doesn't mean that it has to be in the direction of the displacement (which is given by the velocity vector) "Diagonal" motion is just an artifact of a coordinate system, which is arbitrary.

I've got one at work My G4 cube was neat looking, but needed to be replaced, and is now happily toiling as our fax server.

Mac G4 dual 867 MHz, 1 GB RAM.

e is the fraction of the original energy (measured above the first step, or mgH) that is retained. You should be able to set up a simple equation with that information.

If you want the bounce height relative to the stairs to be equal, then the ball has to lose the energy it gained in one step on each bounce. So if the height of a step is a, it loses mga of energy in each bounce.

There's not an absolute cutoff, though, so the choice is somewhat arbitrary for saying what the visible range is. The eye efficiency looks sorta gaussian, but a lot of the time a linear scale is shown, rather than a log scale, which makes it look like the efficiency goes to zero at 400nm and 700nm. I've used lasers at 780 nm and could see diffuse reflections at low power (a few mW). I've also seen 852 nm light (a few hundred mW source) which made me realize that I wasn't wearing my laser goggles.

The drag depends only on the speed of the object. If you increase your thrust, your speed will increase but then so will the drag, until you reach the speed where they are equal. Then the net force will be zero, and speed will be constant.

This is called anomalous dispersion. No violations of causality occurred.

Evolution doesn't have to be gradual to that extent. A mutation that proves to be beneficial will tend to spread through a population and this will take time, but not necessarily millions of years. (Keep in mind that it's really the number of generations that matter, and many organisms have shorter life cycle times than humans do.)

I think any of the noble gases will act like ideal gases, since they don't form molecules. Others will too, to varying degrees.

A ml is a cm3

The drag equation uses v2 because the force depends on the square of the speed. If you go twice as fast, the drag is 4 times bigger. That's what has been observed to hold. You don't use v because it doesn't depend linearly on v. There is probably a theory that shows why the term is v2, but if anyone here knew it they'd probably have posted it by now. If I had to guess, I'd say that it's a combination of imparting momentum to air molecules by collision, which depends on the relative speed, and trying to compress/do work on the air (or whatever fluid) which would also depend on the relative speed. So you end up with a combination of the two effects, which is nonlinear and thus depends on v2. Again, this is a guess.

Interesting in what way?