Hard Definition and 1000 Threads

Homework Statement \int_0^1 \frac{x^4(1-x)^4}{1+x^2}\ dx The Attempt at a Solution A gonio substitution gets nasty really fast moreover the differentiation under the integral sign trick doesn't seem to give more insight (at least that's what I think). Integration by parts gets a ln(.) times...

Homework Statement Five dice are rolled. You win a dollar for each number other than a five that is rolled, but you don't win extra for duplicate numbers; for example if [3,5,3,2,1] is the result, then you win three dollars. What should you pay to play this game (what is expected value)...

Homework Statement \int_{0}^{\pi/4} \exp \left(-\frac{1}{\cos^2x}\right)\mbox{d}x The Attempt at a Solution Can someone give me a hint? I don't see a smart substitution nor a path via integration by parts...

Greetings, I am 14 years of age and I am thinking of choosing a profession revolving around neuroscience. My query is how hard is it to enroll in the related university and how much work does it require? -Thanks

I have to choose what I want to do in university and I was wondering how smart you have to be to do theoretical physics. I do maths , applied maths and physics in school and I'm good at all of them. Any help is very much appreciated.

Homework Statement A computer is reading data from a rotating CD-ROM. At a point that is 0.030 m from the center of the disc, the centripetal acceleration is 120 m/s2. What is the centripetal acceleration at a point that is 0.050 m from the center of the disc? Homework Equations ac =...

Two identical blocks are tied together with a string and placed along the same radius of a turntable that is spinning about its center. The inner block is 4 cm from the center and the outer block is 5 cm from the center. The coefficient of static friction between the turntable and the blocks is...

Homework Statement "During workout, the football players at (insert generic college here) ran up the stadium stairs in 66 seconds. The stairs are 140m long and inclined at an angle of 32 degrees. If a typical player has a mass of 95 kg, estimate the average power output on the way up...

Construct an isomorphism A4 (AND) D4 ---> (Z/2,+)X(Z/2,+) where D4's the symmetries of the square so I found D4(And)A4={(13)(24),Id,(12)(34),(14)(23)}

Really hard Volume Question. URGENT! Can someone help me with this question? I don't know where to begin. I don't want the answers, just hints in the right direction *edit* can a mod please fix the topic title? It's supposed to read 'Really hard Volume Question. URGENT!' << Done. >>...

A thick spherical shell of charge Q and uniform volume charge density p is bounded by radii r1 and r2, where r2 > r1. With V = 0 at infinity, find the electric potential V as a function of the distance r from the center of the distribution, considering the regions (a) r > r2, (b) r2 > r > r1...

Homework Statement First z(t) + (-tz + 3t)dt=0 Second: in attachment Homework Equations How can one solve hose integrations I was faced as one part in solving Dif. equation. The Attempt at a Solution I have tried to soleve bouth of them by usin substitution rule but I have failed do...

hello all, im doing a research on model called RABR which supports dark and bright solitons. as first step i need to find numeric solution for the following equation: F'' = c1*F - c2*F/sqrt(c3+F^2) where c1, c2 , c3 are const, and F is function of x, i.e: F= F(x) i try to make...

Homework Statement Let f(x) be defined and differentiable on the entire x-axis. Show that if f(0) = 0 and everywhere |f'(x)| <= |f(x)|, then f(x) = 0 identically. Homework Equations The Attempt at a Solution I didn't really know how to get started, but as I worked through the problem, I...

Homework Statement A person standing at the top of a hemispherical rock of radius R kicks a ball (initially at rest on the top of the rock) to give it horizontal velocity vi (a) What must be its minimum initial speed if the ball is never to hit the rock after it is kicked? (b) With this...

Hello, this question is about symmetry of polar coordinates. For a polar-curve to be symmetric around the x-axis we require that if (r,a) lies on the graph then (r,-a) or (-r,Pi-a) lies on the graph. To be symmetric about the y-axis we require that (-r,-a) or (r,Pi-a) lies on the graph...

1. Homework Statement You are on an island, and you reach a fork in the road. You want to go to the Cuddly-Wuddly tribe, not the Nasty-wasty tribe. Cuddly-Wuddlies always tell the truth, while Nasty-Wasties always lie. A man is standing in the middle of the road, but you don't know what tribe...

Homework Statement Imagine a tank traveling at constant speed v1 along direction AB and a missile is chasing the tank with constant speed v2. The direction of motion of the missile is always pointing toward the tank. At the t the tank is at position F and the missile is at position D, where FD...

Gizmag directed me to a website where the following ad appears. I don't think that quoting it violates copyright, since the owners of it want it to be seen, but the Moderators should probably vet it anyhow. The reason that I'm posting it is because I'm very interested in buying one, but I'm...

Homework Statement An object with a charge of +4.0 x 10^-18 C and a mass of 1.1 x 10^-15 kg is held stationary by balanced gravitational and electric forces midway between horizontal charged plates. What is the applied voltage V? Homework Equations The Attempt at a Solution I...

Hello guys, I am asking this out of complete curiosity, as I am not in the position yet to need to know this information. I was wondering if it is harder to get into a top tier school for graduate or for undergraduate? It seems to me that graduate would make more sense, its higher education so...

Hi PF, What are the major difficulties the man faces when he tries to reach the Moon? Is it because he has to return to Earth, so that the difficulties are more than doubled? Because the distance between the Earth and the Moon is not that big compared to Earth's equator circumference (less...

Recently I've gained interest in reading the classical works of mathematicians and physicists and came to the realization that knowing Latin would be of great use. Is it worth the effort to learn the basics necessary to comprehend for example Gauss' works, or might I just as well get the...

A 46-g golf ball flies off at 1.5 times the velocity of the clubhead that struck it. a) Show that the mass of the clubhead was 138g. b) What proportion of the clubhead's initial kinetic energy was transferred to the ball?

Have a hard time grasping the concept of the Geodesic. If you are given a velocity and position of say a small astroid entering the gravitational field of the Earth. How do you find the trajectory or path it takes as it falls to Earth? Not afraid of tensors and advanced calculus.

I have resigned to make this the last in my series of question for the forums. I think it might end up being the most important one and hope others will find it useful. What are some tips, or pointers to resources for tackling a higher work load/ difficulty in classwork than you are used to...

HELP ! this problem is very very confusing T_T Three forces, each of which is perpendicular to the other two, act on an object. If the magnitudes of these forces are 6 N, 15 N, and 10 N, respectively, find the magnitude and direction of the resultant. (State the angles that the resultant...

Hard General Relativity question, help :(!? I cannot come up with a solution to the following, can some one please help me? I would greatly apprecieate it! Thank you! Question 1 The Kretschmann curvature scalar is defined to be K = R_abcdR^abcd where Rabcd is the Riemann tensor. Compute...

I have an external Western Digital 320gb hard drive that has never given me problems. However the only thing i can think of that has caused sudden problems for this external SATA drive is the bios flash that i recently updated. The drive is recognized in mycomputer, however it doesn't say how...

Homework Statement Alright, so I've given this guy a few cracks, and I think I'm close to it, but apparently I'm not right, so here's how it goes. Simple in concept. A meteor moves toward the solar system with speed v0 in a direction such that it would miss the sun by a distance d if it...

I am really stuck on this problem. This entire section I have been teaching myself using the homework answers but I have no idea where to start. Thanks anyone. Question: A beam of thermal neutrons emerges from a nuclear reactor and is incident on a crystal as shown below. The beam is Bragg...

Hey folks, I am thinking about maybe trying to do a physics major. However, I don't want it to be too hard and lower my already low gpa. How hard is the math and courses like upper division Moldern Physics, Mathematical Physics,Dynamics,Thermal Stat, E&M and QM? Also how hard are the require...

Homework Statement By resolving the momentum equations parallel and perpendicular to the incident beam direction, show that α is related to the speed v2 of the recoiling particle by: cos α = m2*v2/(2μ*u1) where μ=m1m2/(m1+m2) Homework Equations See attachment for diagram...

Homework Statement I have read the chapter twice and I have read through the notes several times to help me with the homework assignment. It deals with damped Harmonic Oscillations. Problem: You have a mass submerged horizontally in oil and a spring with a k of 85 N/m pulls on a mass of...

A uniform, 4.0-meter long beam weighing 1200 N is supported by a cable. The beam pivots at the bottom, and a 2100 N dead weight hangs from its top. Since the beam is not accelerating, you know that the net torque on it is zero. Find the tension in the cable, which is oriented at 25° from the...

Homework Statement A golf ball with an initial angle of 30° lands exactly 216 m down the range on a level course. Homework Equations x=vt+.5at2 The Attempt at a Solution

Homework Statement neither my professor nor my TA could figure this out. so they are offering fat extra credit for the following problem Let n be a positive integer greater than 1 and let p1,p2,...,pt be the primes not exceeding n. show that p1p2...pt<4n The Attempt at a Solution...

Homework Statement A computer hard disk starts from rest, then speeds up with an angular acceleration of 198 rad/s2 until it reaches its final angular speed of 7683 rpm. How many revolutions has the disk made 10.7 s after it starts up? Homework Equations t=wf/a delta0=wi*t+(1/2)(a)t^2...

I am stuck on an intergration and can't get a simple answer which i should get p = (2*m*l^2)^(1/2)*(E+m*g*l*cos theta)^(1/2) using small angle (need for question) cos theta = 1 - (theta^2 )/2 Then I intergrate from 0 to 2*Pi and get some very large eqn using a maths program, I can't...

Homework Statement A train traveling at a constant speed rounds a curve of radius 235 m. A chandelier suspended from the ceiling swings out to an angle of 17.5° throughout the turn. What is the speed of the train? Homework Equations a=v^2/r use of cosine and sine v=2x3.14xr/T The Attempt...

Rate of change problem...very hard...please help! Homework Statement The hands on a clock are of length 5 inches(minute hand) and 4 inches(hour hand). How fast is the distance between the tips of the hands changing at 3:00? The Attempt at a Solution Let the coordinates of the two hands...

You throw a ball toward a wall at speed 24.0 m/s and at angle θ0 = 43.0° above the horizontal (Fig. 4-35). The wall is distance d = 16.0 m from the release point of the ball. (a) How far above the release point does the ball hit the wall? What are the (b) horizontal and (c) vertical components...

I bought a book on C++ that was recommend by a friend and a cheap book on C and I just can't get into it. It start off ok, but then the throw 50 lines of code at you for even a basic program and I get lost... I don't know what any of it means and I feel like bashing my head in. Any...

Hi, folks, I need the proof of following inequality for a,t\in(0,1): Weaker form: \ln(1+t^a)\geq a\ln^a(1+t). Stronger form: \ln(1+t^a)\geq\frac{1+a}2\ln^a(1+t).

I'm planning to do a degree in physics (in the U.K) next year. Its just a normal physics course (e.g. not physics with nanoscience, or theoretical physics) and I want to know how hard people think it will be. I'm good at physics and I can grasp concepts quite well. I'm ok at maths, I understand...

Homework Statement What maximum power can be radiated by a 14cm -diameter solid lead sphere? Assume an emissivity of 1 Answer in two sig fig. Homework Equations ( Q / delta t) = e*σ*A*T^4 e=1 σ=5.67*10^-8 W/m^2*K^4 Stefan-Boltzmann constant (<--- who happens to be my great...

ANALYSIS --Really hard ..Please help me Are these TRue or FALSE I am trying to figure it out for 3 hours now and I am really stuck 1) For all x and all y, there exists a z such that x+y=z I know is True 2) For all x there exists a y such that for all z, x+y=z I think this is true...

Electric Field hard question :( Homework Statement What is the electric field between two parralel plats, each of area 1 m^2 which are separated by a distance of 0.01 m, if each plate is charged equally but oppositely with a charge of magnitude 8.84 x 10^-8 C? Homework Equations E= kQ/...

hard complex reasoning help! Homework Statement American advertising agency McKAnn decided to bungee jump a car off a bridge to show how well made the car was. They used a 30 m m rubber bungee cord used by the army to bungee tanks during air drops. it had nine individual cords each around...

Of the pictures I have seen with the Palin family brandishing guns, the majority show hard liquor being drunk or having been consumed. Even the NRA would not condone anyone handling weapons while intoxicated. What does this say about the mindset of someone seeking to be entrusted with the...