Liu

Does anyone know how to do the following question?

Two trains approach the train station from opposite sides each moving at an initial

velocity of 120 km/h with respect to the station and slowing down to a halt in 20

seconds. If both trains are whistling at 5000 Hz, find the distance between the zero

and first order maxima as a function of time.

Please explain the meaning of "first order maxima", as well as show your working or at least give an explanation of how to approach this question. Thanks!

Hi please help to solve the following questions from a physics competition:D

1. Two trains approach the train station from opposite sides each moving at an initial

velocity of 120 km/h with respect to the station and slowing down to a halt in 20

seconds. If both trains are whistling at 5000 Hz, find the distance between the zero

and first order maxima as a function of time.

2. The rockets of the Goths and the Huns are each 1000 m long in their respective rest

frame. The rockets pass each other, virtually touching, at relative speed of 0.8c.

The Huns have a laser cannon at the rear of their rocket that shoots a deadly laser

beam at right angles to the motion. The captain of the Hun rocket wants to send

a threatening message to the Goths by “firing a shot across their bow.” He tells his

first mate, “The Goths rocket is length contracted to 600 m. Fire the laser cannon

at the instant the nose of our rocket passes the tail of their rocket. The laser

beam will cross 400 m in front of them.” But things are different from the Goths’

perspective. The Goth captain muses, “The Huns’ rocket is length contracted to

600 m, 400 m shorter than our rocket. If they fire the laser cannon as their nose

passes the tail of our rocket, the lethal laser blast will go right through our side.”

The first mate on the Hun rocket fires as ordered. Does the laser beam blast the

Goths or not? Resolve this paradox. Show that, when properly analyzed, the

Goths and the Huns agree on the outcome. Your analysis should contain both

quantitative calculations and written explanation.

3.A vertical cylindrical container contains some helium gas that is in thermodynamic

equilibrium with the surroundings. The gas is confined by a movable heavy piston.

The piston is slowly elevated a distance H from its equilibrium position and then

kept in the elevated position long enough for the thermodynamic equilibrium to be

reestablished. After that, the container is insulated and then the piston is released.

After the piston comes to rest, what is the new equilibrium position of the piston?

4. The job of the Stanford Linear Accelerator Center (SLAC) in the United

States is to accelerate electrons to very high energies, to crash these electrons

into things and then to see what happens. The acceleration is accomplished

with a 3.2 km long linear accelerator (linac) which is capable of accelerating

electrons such that each electron will have energy of 50 GeV at the exit point

of the accelerator.

i. Assuming that the electrons accelerate constantly down the linac, what

is the speed of the electron after going 1 m down the accelerator?

ii. When the electrons exit the linear accelerator, magnets are used to curve

the electron beams. Construction plans indicate that the radius of the

curvature is 280 m. By considering the momentum of these now relativistic

electrons, what is the minimum magnetic field required to curve the

electron beams?

5. Canal rays, i.e., positive ion rays are generated in a gas discharge tube. How

often does an ion (r = 0.05 nm) collide with an atom of the ideal filler gas

(r = 0.1 nm) if it travels 1 m in a straight path through the discharge tube

and if the pressure in the tube is 1 mbar? 1 mbar corresponds to 102 Pa. All

the particles are assumed to have the same velocity.

Please show the working or at least give an explanation of how to proceed to the answer. Thanks!

Hi can someone help to do questions 7,8,9 and 10 (b)ii in the following link? Thanks!

http://pic.sgchinese.org/attachments/forum/201109/...