I read that Cerenkov radiation is caused by charged particles traveling faster than the speed of light in the medium, but I don't understand why. I have seen analogies to a plane moving a supersonic speed creating a cone of sound waves because the waves can't keep up with the plane, but in this...
Homework Statement
A rocket of rest length 100 meters is moving at .6c relative to Earth and contains an astronaut at the tail end of the ship. The astronaut fires a bullet toward the front of the ship. The velocity of the bullet relative to the astronaut is 0.8c. How much time does it take the...
I want to get clarification on Lenz's Law while I'm doing a problem like this. The magnetic flux decreases because of the shrinking area, so the induced current must have a direction such that its magnetic field is directed downwards, right? So for a square loop, that means that the current is...
Force on a current carrying wire: F = iL x B where i is current, L is the length of the wire, and B is the magnitude of the magnetic field. To get the direction you must do a cross product. The L vector is in the direction of the current and the B vector is downward, so you ultimately get a...
induced voltage = -cos(angle between area vector and B vector) * B * dA/dt. The angle is 0 because they are parallel. dA/dt = distance between rails * speed of axle so voltage = Bvd. Just divide the voltage by the resistance to get the current.
Nope, I don't recall that. I'm still confused about the quantitative parts of this problem. I found the induced voltage and I found the current. I just don't know how to find the force on the moving axle.
Imagine a set of train tracks. Now there is one bridge (a resistor) connecting the two rails in one spot. On a different spot, there is rolling axle that acts as another bridge and it makes good electrical connection with the rails creating a full rectangular circuit. This axle rolls at a...
The problem is dx/dt = (x+9)^2.
This is separable so I made it dx / (x+9)^2 = dt.
The only method I can think of using for something like this is partial fraction, but I can't get it to work with A/(x+9) + B/(x+9).
Can anyone find a method that works?
We see the Geminids as a result of the fragments of the asteroid 3200 Phaethon colliding with the Earth's atmosphere. They are visible every year around December 13-16. As you can see in this NASA simulation (http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Phaethon;orb=1), we pass through the orbit of the...
Homework Statement
A potential energy function is given by U(x) = 4x^2 and I found the total energy to be 7 J. They ask: Graph position vs. time and kinetic energy vs. time using this information and assume that the particle has an initial position of 0.
The Attempt at a Solution
I got the...
Mechanics--Angular Motion and Conservation of Energy
Homework Statement
A uniform bar of mass m and length L is pivoted at one end and is held vertically above the pivot. After the bar is released, it swings downward and clockwise with no friction in the pivot.
At the instant the bar is...
I was looking at the sky last night, and I saw Venus to the west, really high in the sky. It was brighter than any star that night. Why am I able to see it? It seems like, since we are on the side of the Earth facing opposite the sun at night, I should be able to only see the planets that are...