In a nuclear fission reactor, each fission of a uranium nucleus is accompanied by the emission of one or more highspeed neutrons, which travel through the surrounding material. If one of these neutrons is captured in another uranium nucleus, it can trigger fission, which produces more fast neutrons, which could make possible a chain reaction. However, fast neutrons have low probability of capture and usually scatter off uranium nuclei without triggering fission. In order to sustain a chain reaction, the fast neutrons must be slowed down in some material, called a “moderator.” For reasons having to do with the details of nuclear physics, slow neutrons have a high probability of being captured by uranium nuclei.

A slow neutron induces fission of U-235, with the emission of additional (fast) neutrons. The moderator is some material that slows down the fast neutrons, enabling a chain reaction.

In the following analyses, remember that neutrons have almost no interaction with electrons. Neutrons do, however, interact strongly with nuclei, either by scattering or by being captured and made part of the nucleus. Therefore you should think about neutrons interacting with nuclei (through the strong force), not with entire atoms.

1. Based on what you now know about collisions, explain why fast neutrons moving through a block of uranium experience little change in speed.

2. Explain why carbon should be a much better moderator of fast neutrons than uranium.

3. Should water be a better or worse moderator of fast neutrons than carbon? Explain briefly.

A transverse sinusoidal wave is generated at one end of a long, horizontal string by a bar that moves up and down through a distance of 1.7 cm. The motion is continuous and is repeated regularly 160 times per second. The string has linear density 460 g/m and is kept under a tension of 140 N. Find the maximum value of (a) the transverse speed u and (b) the transverse component of the tension T. (c)Show that the two maximum values calculated above occur at the same phase values for the wave. What is the transverse displacement y of the string at these phases? (d) What is the maximum rate of energy transfer along the string? (e) What is the transverse displacement y when this maximum transfer occurs? (f ) What is the minimum rate of energy transfer along the string? (g) What is the transverse displacement y when this minimum transfer occurs?

A.)

In the lab, you will determine a value for the time constant of the RC circuit, by measuring the amount of time it takes the capacitor voltage to increase from 0.0 V to ______ % of its maximum value.

B.)

If you only have capacitors of one value, you can change the total capacitance of the circuit by using combinations of capacitors. Assuming that all the capacitors have the same value, how could you increase the total capacitance?

Options:

B) A 1300 -kg car is pushing an out-of-gear 2200 -kgtruck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push horizontally against the ground with a force of 4500 N . The rolling friction of the car can be neglected, but the heavier truck has a rolling friction of 760 N , including the "friction" of turning the truck's drivetrain. What is the acceleration aT of the truck?

C) An 89.0 kg spacewalking astronaut pushes off a 620 kg satellite, exerting a 85.0 N force for the 0.540 s it takes him to straighten his arms. How far apart are the astronaut and the satellite after 1.50 min ?

A microscope has an object lens f=11 mm and an eyepiece lens f=22 mm separated by 122 mm. Where is the image of the eyepiece located? What is the magnification?

Can you give 2 othere examples of a diagnostic radiopharmaceutical, there uses and desirable radiological and biological properties.

e.g - sodium pertechetiate 99m (please don't pick this one again);

Under electrostatic condition electric charge Q = 17.7x10-9 C is uniformly distributed on the surface of an isolated conducting sphere of radius R = 3 m. There is no other charge around. (a) What is the electric flux through a concentric spherical surface of radius 2R. (b) What is the electric potential at the surface of the conducting sphere? What is the electric field inside the conducting sphere? Please explain the steps and formuals .Mandatory !!

The temperature in Winterberg is a sinusoidal function in time. 120 days ago, the temperature was at its maximum value of 55◦F. The tempearture has been falling since then, and 20 days from today it will reach its minimum value of 10◦F.

(a) Write a function f(t) in sinusoidal standard form for the temperature in Winterberg, in Fahrenheit, t days from today

b)People can only ski when the temperature is below 28◦F. Over the next 700 days (starting today), for how many days is it cold enough to ski? You can round all your answers to the nearest day.

A positive charge q is fixed at the point x=0,y=0 and a negative charge -2q is fixed at the point x=a,y=0.

Part A:

Derive an expression for the potential V at points on the y-axis as a function of the coordinate y. Take V to be zero at an infinite distance from the charges.

Part B:

At which positions on the y-axis is V = 0?

Part C:

What does the answer to part A become when y>>a?

Part D:

Explain why this result is obtained.

A parallel plate capacitor with plate separation d is connected to a battery. The capacitor is fully charged to Q Coulombs and a voltage of V. (C is the capacitance and U is the stored energy.) Answer the following questions regarding the capacitor charged by a battery. For each statement below, select True or False.

After being disconnected from the battery, inserting a dielectric with κ will increase U.
With the capacitor connected to the battery, decreasing d increases U.
With the capacitor connected to the battery, inserting a dielectric with κ will increase C.
With the capacitor connected to the battery, increasing d increases C.
After being disconnected from the battery, increasing d decreases V.
After being disconnected from the battery, inserting a dielectric with κ will decrease V.

We did an experiment : determination of entropy changes during melting of ice in a closed system. Can you write a 400 words paragraph introduction about The Second Law of Thermodynamics, entropy, entropy changes in reversible and irreversible processes, methods of calculating entropy changes in isothermal, isobaric and isochoric processes and entropy of the phase transformation.

In your own words. No copy-paste from the internet. Pleasee!!

In forensic science, it is useful to measure the speed at which firearms propel bullets. Before modern instruments, this was done with a device called a “ballistic pendulum”, consisting of a block of some soft material hanging from the end of a string. The experimenter fires a bullet into the block, which lodges into it; the block swings up at an angle. By measuring the angle, the experimenter can determine the velocity of the bullet.

Suppose that you are a detective trying to measure the velocity of the bullets fired from a particular gun. You construct a ballistic pendulum out of a string of length 50 cm and a clay block of mass 2 kg, and fire a bullet into it. If the bullet has a mass of 2.6 grams and the pendulum swings up to an angle 13.4 degrees, how fast was the bullet traveling when it struck the block?

Show all work and Thanks in advance!

Derive the energies for an infinite square well potential. Start from the Schrödinger Equation and show your work.

Please show all the work and steps and the math in details.
similar problem will be on my Exam, So I want to learn how to do this. Please write clear so I can read it.

Design a "bungee jump" apparatus for adults. A bungee jumper falls from a high platform with two elastic cords tied to the ankles. The jumper falls freely for a while, with the cords slack. Then the jumper falls an additional distance with the cords increasingly tense. Assume that you have cords that are 14 m long, and that the cords stretch in the jump an additional 20 m for a jumper whose mass is 80 kg, the heaviest adult you will allow to use your bungee jump (heavier customers would hit the ground). (a) It will help you a great deal in your analysis to make a series of 5 simple diagrams, like a comic strip, showing the platform, the jumper, and the two cords at the following times in the fall and the rebound: 1 while cords are slack (shown here as an example to get you started) 2 when the two cords are just starting to stretch 3 when the two cords are half stretched 4 when the two cords are fully stretched 5 when the two cords are again half stretched, on the way up On each diagram, draw and label vectors representing the forces acting on the jumper, and the jumper's velocity. Make the relative lengths of the vectors reflect their relative magnitudes. (b) At what instant is there the greatest tension in the cords? (How do you know?) When the person has fallen between 0 m and 14 m. When the person has fallen between 14 m and the bottom. At the top, when the person has fallen 0 m. At the bottom, when the person has fallen 34 m. When the person has fallen 14 m. (c) What is the jumper's speed at this instant, when the tension is greatest in the cords? v= m/s (d) Is the jumper's momentum changing at this instant or not? (That is, is dpy/dt nonzero or zero?) (e) Which of the following statements is a valid basis for answering part (d) correctly? A very short time ago the momentum was downward (and nonzero). Since the momentum is zero, the momentum isn't changing. If the momentum weren't changing, the momentum would remain zero forever. Since the net force must be zero when the momentum is zero, and since dpy/dt is equal to the net force, dpy/dt must be zero. After a very short time the momentum will be upward (and nonzero). the tolerance is +/-5% (f) Focus on this instant of greatest tension and, starting from a fundamental principle, determine the spring stiffness ks for each of the two cords. ks= N/m (g) What is the maximum tension that each one of the two cords must support without breaking? (This tells you what kind of cords you need to buy.) FT= N (h) What is the maximum acceleration |ay|=|dvy/dt| (in "g's") that the jumper experiences? (Note that |dpy/dt|=m|dvy/dt| | if v is small compared to c .) |ay|= g's (acceleration in m/s2 divided by 9.8 m/s2) (i) What is the direction of this maximum acceleration? (j) What approximations or simplifying assumptions did you have to make in your analysis which might not be adequately valid? (Don't check any approximations or simplifying assumptions which in fact have negligible effects on your numerical results.) Assume that the gravitational force hardly changes from the top of the jump to the bottom. Neglect air resistance, despite fairly high speeds. Assume the speeds are very small compared to the speed of light. Assume tension in cord proportional to stretch, even for the very large stretch occurring here.