Minimum Definition and 1000 Threads

Homework Statement A circuit employs a silicon solar cell to detect flashes of light lasting .25 seconds. The smallest current the circuit can detect reliably is .42 \muA. Assuming that all photons reaching the solar cell give their energy to a charge carrier, what is the minimum power...

Homework Statement Suppose that f(z)=(z-1)(z-4)^2. Find the lines through z=2 on which |f(z)| has a relative maximu, and those on which |f(z)| has a relative minimum, at z=2. Homework Equations Maximum Modulus Theorem And Minimum Modulus Theorem The Attempt at a Solution So I know...

Homework Statement r(t) = < t^2, 6t, t^2 − 24t > Using this position vector, find the minimum speed of the particle. Homework Equations v(t) = r'(t) The Attempt at a Solution I've found similar topics with similar problems but I'm having a hard time figure mine out. I know...

Homework Statement A 5.0 kg mass is held against a wall with which it has a coefficient of static friction of 0.85. What is the minimum horizontal force required to hold the mass against the wall ? The teacher said answer is 58 N .. i can't get to that answer.. Homework Equations...

Homework Statement The Attempt at a Solution I have worked my brain out but can't work out the problem the normal force will act through th center of mass right? if not please some one tell me why !

Homework Statement Use the formula: n=(sin(A+D)/2)/(sin(A)/2) to find D for an equilateral prism of index of refraction n=1.50 (where A=apex angle for a prism=60 degrees in this case, and D=minimum angle of deviation) Homework Equations Snell's Law: (n1)sin(i)=(n2)sin(r)...

Homework Statement A SMALL CONE FILLED WITH WATER OF RADIUS 4M AND THE WATER DOESNT FALL DOWN. WHAT MUST BE THE MAXIMUM PERIOD OF REVOLUTION Homework Equations The Attempt at a Solution I AM CONFUSED! HOW TO APPROACH THE PROBLEM? SHOULD FIRST CALCULATE THE MINIMUM VELOCITY...

Homework Statement Find the Dimensions of the right circular cone of minimum volume which can be circumscribed about a sphere of radius 8 inches.Homework Equations N/A The Attempt at a Solution So this is my try, i did the question to find the minimum volume of the cone, For Larger Size...

Homework Statement A balloon contains gas of density pg and is to lift a mass M, including the balloon but not the gas. Show that the minimum mass of gas required is m= Mp / (pa - pg). Where pa is Atmospheric density Homework Equations I assume fluid motion so P= Po + p*h*g Also...

Homework Statement A rectangular field to contain a given area is fenced off, along a stright river. if no fencing is required along the river, show that the lest amount of fencing will be required when the length of the field is twice its width. Homework Equations N/A The Attempt...

Hello. As stated in the title, I have a function y that is in terms of x. How do I go about determing the 'x' that makes 'y' a minimum? Thanks!

Homework Statement I have a 2D square well with sides a. What is the minimum momentum and energy for this well? Homework Equations Minimum momentum given by Δp≈ℏΔx and Δp≈ℏΔy Minimum energy given by ΔE≈ℏΔt This might be right. It says to consider the Schrödinger Equation in 2D. I've never...

Homework Statement Suppose F: Rn --> R has first order partial derivatives and that x in Rn is a local minimizer of F, that is, there exists an r>0 such that f(x+h) \geq f(x) if dist(x, x+h) < r. Prove that \nabla f(x)=0. Homework Equations We want to show that fxi(x) =0 for i = 1,...,n So...

I am wondering what the minimum sampling duration must be in order to accurately resolve a 60Hz wave. I know the FFT works with periodic waves about the number N but I am not sure how this relates to say a sampling duration that is 1 half the sampling period of a 60 Hz wave. I'm worried that the...

Homework Statement Use the method of Lagrange multipliers to find the points on the ellipse (x^2)+(2y^2)=2 that are closest to and farthest from the line x-y=2. Homework Equations I know that to do the lagrange I have to take the gradient of a function f and set it equal to some unknown...

So i have the points A=(1,0,1) and B=(1,-1,0) and the third corner lies on the line L:(x,y,z) = (t,t,t) and i need to find a triangle with the minimum area possible. My initial approach was to calculate the vector BA and BC and then apply both vectors in the area triangle formula...

Homework Statement 433J of heat is extracted from a massive object at 0\circC while rejecting heat to a hot reservoir at 19\circC. What minimum amount of work will accomplish this? Answer in units of J. Homework Equations COP= Qc/(Qh-Qc) = Tc/(Th-Tc) The Attempt at a Solution...

Homework Statement Find the shape of the solid of revolution with the minimum moment of inertia about it's axis, given the volume is fixed. Homework Equations I=\int\frac{1}{2}r^2dm=\int\frac{1}{2}r^2\rho~dV=\int\frac{\rho\pi}{2}r^4dz V=\int \pir^2dz I+\lambda V must be stationary. The...

I cannot seem the crack this problem. The solution may be trivial, but normal methods of max/min do not seem to work. Thanks for your help. Homework Statement Suppose it to be known that consumption of coal by a certain ship may be represented by the formula y = 0.3 + .001v3 Where y...

Hello, I am working on a project and I came across a question that is a little beyond my skill set. I am designing a support for a roof, and I have the force into the post, the length of the post and I need to determine what pipe I need, size, schedule diamter, etc. How do I go about this...

Hello Just had a quick question for a structures class. When attempting a problem, what's the main difference between applying PVW and PMPE? What would classify a problem in using one over the other? Thanks

Hi, nice to meet everybody here at physicsforums.com! I'm JM92 and I have a physics problem I need help with. Homework Statement Find the smallest value of the mass M for which the system will remain at rest given that the coefficient of static friction is 0.100...

Homework Statement 2 arms of a u-tube are not identical, one having twice the diameter of the other. a cork in the narrow arm requires a force of 16n to remove it. the tube is filled with water and the wide arm is fitted with a piston. the min force that must be applied to the piston to push...

Homework Statement A spark occurs at the tip of a metal needle if the electric field strength exceeds 3.0x10^6 N/C. What is the minimum surface charge density for producing a spark? Homework Equations int(EdA) = (Qin) / e0 The Attempt at a Solution I imagine the surface as a cylinder with...

Homework Statement <In Pic 1> Homework Equations (1/2)mv2 = ΔU The Attempt at a Solution I thought that if i apply the equations i'll have my answer but i got 2.5m/s while answer is 3m/s Please refer the solution given by some book --- Pic2, Pic3 <sorry for bad image, my...

So no one is quite sure that P != NP, although they tend to favor that relation. But I was curious, has anyone proved a minimum degree order to any algorithm that solves NP complete problems in polynomial time? In other words, they don't know if it can be done in polynomial time, but do they...

I am having trouble understanding (not for homework) what a wave packet is in terms of the correspondence of the idea of a wave packet to a "point like" particle. I'd like to focus on the 1d wave packet ultimately, but in order to describe my consternation -- let me detour to a well defined...

Is life most likely to start near greatest statistical mechanical order? For instance, DNA's extended regular structure might relate lowest entropy for its molecular weight. Is biochemical replication the antithesis of randomness? Does the apparent rarity of life in the universe reflect the...

Minimum change in velocity! Helpppp? Homework Statement Calculate the minimum change in velocity (delta V or ∆V) required for the Space Shuttle to decrease its altitude to 60 miles if it’s orbiting with an apogee of 236 miles and a perigee of 215 miles above the surface of Earth. Use the...

Homework Statement A collapsible plastic bag contains a glucose solution. If the average gauge pressure in the vein is 15000 Pa, what must be the minimum height of the bag in order to infuse glucose into the vein? Assume that the specific gravity of the solution is 1.04. The acceleration of...

[(there is an option that there is no Local minimum or Maximum point in this Function) BUT i need to show the way. thanks.

Homework Statement Find the max and min values of the function f(x, y) = (x-y)/(2 +x2 + y2) over the disk x2 + y2 <= 4 Homework Equations The Attempt at a Solution fx = 1/(2 +x2 + y2) + -2x(x-y)/(2 +x2 + y2)2 = (2- x2 + y2 +2xy)/(2 +x2 + y2)2 Should equal zero when x=1 y=...

Homework Statement From a square piece of cardboard, 30 cm on each side, an open topped box is to be constructed by cutting the squares from the corners and turning up the sides. What are the dimensions of the box of largest volume? The Attempt at a Solution I know how to do...

Homework Statement Our lab was to predict the distance a bungee jumper will fall before coming to rest. I already found the spring constant When we have the spring constant we had to find the minimum safe drop height for a bungee jumper before being stopped by the spring. The following...

Homework Statement As in the attachement, find the minimum v such that the ball does not touch the rock. The Attempt at a Solution The solution given is mg*cos(theta) - mv^2/R = n < 0, where theta is the angle between the ball and the person. My question is why is there a normal...

Homework Statement of f(x) = \sum | x - a_i | ( i = 1 to n ) where a_1 < a_2 < ... < a_n The Attempt at a Solution I believe I have proven that if n is odd then the minimum is as ceiling a_(n/2) or a_(n+1)/2. The book says a_(n-1)/2 though, but I think it's wrong.. if...

I was wondering, if you have a non-conservative vector field (so that the line integral of each path from point A to point B isn't the same) that represents some sort of force, then is there a method to find the path that requires the least amount of work from a designated point A to point B...

(a) Two stars are photographed utilizing a telescope with a circular aperture of diameter of 2.42 m and light with a wavelength of 547 nm. If both stars are 1022 m from us, what is their minimum separation so that we can recognize them as two stars (instead of just one)? theta=1.22*...

a cylinder has two identical cones one each end. the volume of the object is 50(pie/3) find the total height. so 2h+k=height. where to from there

Homework Statement Nine students A, B,..., I serve as members on eight committees, as follows. Committee 1: A, B, C, D Committee 2: A, C, D, E Committee 3: B, D, F, G Committee 4: C, F, G, H Committee 5: A, H Committee 6: H, I Committee 7: G, H Committee 8: E, I Each committee is to meet...

Using basic statics determine the minimum load required on a rock anchor to restrain a cube with a volume of 30 m3 if it were resting on a discontinuity with an angle of 60 degrees. The Attempt at a Solution the cube in question is meant to be a cube of granite. it has a density of 2700...

Homework Statement Find the maximum and minimum of the function f over the closed and bounded set S. Use langrange multiplier method to find the values of the boundary points. Homework Equations f(x,y) = (1+x+y)2 S = {(x,y) : x2/4 + y2/16 <= 1} The Attempt at a Solution...

Homework Statement Find the absolute maximum and minimum values of f on the set D. f(x,y) = 1+4x-5y D is the closed triangular region with vertices (0,0) (2,0) (0,3) Homework Equations To find the absolute maximum and minimum values of a continuous function on a closed, bounded set : 1. Find...

Homework Statement What is the minimum speed of the car must have at the top of the loop? There are three methods. I would like to know which method or answer is correct. Please see attached file. Homework Equations Please see attached file. The Attempt at a Solution Please...

How would you write a proof that proves that the minimum area between a function and its tangent line is the tangent line evaluated at point p, where p is the midpoint on a given interval? i.e. The minimum area between x^2, and its tangent line on the interval [0,1]...

Homework Statement Hi there, motor and generator gurus Suppose a generator has the following specifications, and the rotor turns with frequency 10 Hz. Determine the maximum and minimum value of the voltage generated, using the formula: ε = Βlv n = 1000 loops = 1000 B = 10 Tesla I...

If I understand Brian Greene’s argument (in The Elegant Universe, and repeated elsewhere) for the Planck length being the minimum measurable length based on T-symmetry in string theory, it goes something like this: There are two ways to measure things, one with vibrational energy v and one...

Homework Statement Find the point on the plane x-y+z=4 closest to the point (1,2,3). d=\frac{2}{\sqrt{3}} Homework Equations Hmm... The Attempt at a Solution As you can see, I've already solved for the shortest distance. But, knowing the plane I'm on and the distance, how do I...

Homework Statement A crate of weight Fg is pushed by a force P on a horizontal floor. (a) If the coefficient of static friction is us and P is directed at angle theta below the horizontal, show that the minimum value of P that will move the crate is given by P = ( us*Fg*sec(theta)) / (1...

Homework Statement Hello, one of the things I have to do for my lab report for this week is to prove that the angle between the left and right deviations of the telescope is twice the angle of minimum deviation. Its a lab where you have to find the refractive index of substances using a...