Proportional Definition and 195 Threads

A spherical snowball melts at a rate proportional to its surface area. Show that the rate of change of the radius is constant. Two ratios are proportional if they change equally and are related by a constant of proportionality? Not sure about this definition, but please correct it if you can...

Homework Statement Homework EquationsThe Attempt at a Solution Power is given by F.v , but I am not sure how to calculate F in this case .Again 'v' is the speed of the point of application of force F . I also do not understand how force applied on blades is causing work . Any help is...

The following derives the relation that for a blackbody radiation the energy density is proportional to the energy emitted per unit area over unit time. The average energy density ##d\psi## is obtained by dividing the radiant energy ##dE## received by the surface ##dB## in 1 second by the...

1. Homework Statement Ok, so part i) asks us to state how the magnitude of electric field strength is related to potential gradient, and that I answered electric field strength is potential gradient. Homework Equations Electric field strength E=Q/(4πεr^2) F=Qq/(4πεr^2) Electric potential...

Homework Statement Hi I've been modelling a particle traveling in a particle detector that has a momentum vector Px, Py, Pz which we've conveniently been using Pperpendicular (i.e. in the xy plane) and Pz. I can calculate the distance traveled in the xy plane and I need to calculate the...

Hello, I was doing my physics coursework, and blew a hairdryer at my makeshift aerofoil across distances of about 10cm and wind velocities of 8-11 m/s, then measured the lift off of a balance. I found they were proportional, exactly (!?), after doing some research I found drag is proportional...

Example problem from a Classical Mechanics book. Find the displacement and velocity of a particle undergoing vertical motion in a medium having a retarding force proportional to the velocity. F = m(dv/dt) = -mg-kmv dv/(kv + g) = -dt (1/k)ln(kv + g) = -t + c kv + g = e^(-kt+kc) v =...

Homework Statement I[/B] have some difficulties proving that the ideal gas temperature is directly proportional to absolute temperature defined by the second law of thermodynamics. Homework Equations The ideal gas temp. is defined by the ideal gas equation: pV=NkTi(T), where k is Boltzmann's...

hmm.very thankful to everyone who answered but i think where I am actually getting stuck is nothing high level.im just not getting why a proportional to b and a proportional to c implies a proportional to bc .i get it that if b changes by factor x then a changes by factor x and at the same time...

in particular f=Gm1m2/r^2?sorry if my question sounds very irrelevant.if f is proportional to m1m2 it implies f=some constant times m1m2.okay.at the same time f is inversely proportional to r^2 .so force = some other constant times 1/r^2.okay.but in most places i see that what is done is they...

Say that i were to hold an electric appliance obvious, i receive an electric shock What will 'how bad my injuries will be' depend on ? Is it potential difference, current, heating effect, ...

Lorentz force equation shows us that current is proportional to the force. Is it safe to assume that the force generated by an AC current at 60Hz will always have the same frequency? In other words, as the current increases and deceases (sinusoidal) the force will follow the same pattern at the...

Hi guys. I have a question regarding the expansion of space. Alright, so I know that space expands proportionally to the amount of distance. However, I'm not sure why this occurs. Can someone inform me on that? Additionally, I know any individual placed anywhere in the universe would observe...

If you were to calculate work done by rolling friction of a wood sphere rolling down an incline and compare it to work done by friction of a wood block sliding down an incline, are the values for the coefficient of rolling and kinetic friction somehow proportional to each other? This is for a...

Homework Statement My task is to plan and carry out experiments which show that the resistance of a conductor is proportional to the conductor's length. I have access to the following equipment: http://imgur.com/a/GuqUX Amperemeter, voltmeter, electricity, ruler som other werid things and...

Straight from my physics textbook: For objects moving at high speeds through air, such as airplanes, skydivers, cars, and baseballs, the resistive force is reasonably well modeled as proportional to the square of the speed. In these situations, the magnitude of the resistive force can be...

A. Sound is nothing more than a local disturbance whose propagation is facilitated by the collisions between particles B. The distances between molecules in solids are very small, i.e., solids are more dense - as compared to liquids and gases. Because they are so close, than can collide very...

Do we know if the instantaneous/observed acceleration due to the vacuum is directly proportional to distance or possibly? (ignore any gravitational effects) A~D ? A~D^2 ? A~D^(1/2) ? A~D^(-2) A~D^(Other) ? OR A= constant (edited as I forgot this one) If not, is there a best guess/fit or...

Yeah... I know many of you people might be laughing but still I don't understand how can we simply reach the conclusion that increasing temperature increases the atomic motion. Consider this : When we push something, it moves (don't over think about this one) when we apply torque on something...

Today while reading a book i read that conductance of a metal depends on its density. But it is also dependent on its resistivity. Does that mean that resistivity and conductivity are proportional to each other?

The terminal voltage and current are measured as the resistance is decresed through a cell with emf and internal resistance. Graph of V (y axis) I (x axis) shows straight line decreasing gradient. 1. Explain why terminal pd decreases as the current increases. is terminal pd the same as...

Hi, I've been thinking about how to calculate a permeability curve, I thought this would be an easy to find online but unfortunately I haven't had any luck. From what I can graphically see below: It appears to me that mu for a ferromagnetic material is proportional to the derivative of B vs H...

Hi! :o I'm stuck :confused: I was thinking I need to use the equation $f=kw^2$ but I'm really not sure.

Hi guys. I have a problem with my spectrum and I would like your help. I have a system with a proportional Gas detector (krypton gas), preamplifier and amplifier, Co57 source, and the last two months the spectrum has gotten worst as you can see in the attachment. Does anyone know what might be...

Homework Statement FIGURE 9 shows the block diagram of the control of an electric heatingsystem. The heater is driven from a voltage-controlled power supply, the voltage V1 being derived from a potientiometer. The output temperature, θO, is subject to disturbances, θD, because of changes in...

Homework Statement I'm struggling with the problem below: If E_n^{(0)} \ \ (n\in \mathbb N) are the energy eigenvalues of a system with Hamiltonian H_0=\frac{p^2}{2m}+V(x) , what are the exact energy eigenvalues of the system if the Hamiltonian is changed to H=H_0+\frac{\lambda}{m} p \ ...

Homework Statement FIGURE 5 shows a proportional plus derivative controller that has aproportional band of 20% and a derivative action time of 0.1 minutes. Construct the shape of the output waveform for the triangular input waveform shown, if the input rises and falls at the rate of 4 units...

Homework Statement An object starts from rest at the origin and moves in the positive x direction. The velocity is proportional to the displacment. I am trying to find the equation linking velocity to displacement. Homework Equations Since the object starts at rest and then moves in the...

I am trying to build a circuit using gears, motors, and relays only which mimics the motion of a proportional linear solenoid i.e. Hold a spring compressed at a certain distance depending on the current passed, and push/ release it further based on the increase/ decrease of current. (V=12 V...

I'm not really sure where to put this question, but definitely this is just an introductory physics coursework. Let me refresh you first with the basics of the photoelectric effect. We all know that in the photoelectric effect the stopping voltage is just the kinetic energy obtained by the...

Logarithms N 0 1 2 293 46687 46702 46716 294 46850 46835 46864 295 46982 46997 47012 Prop. Pts 1 1.6 2 3.2 3 4.8 4 6.4 5 8.0 6 9.6 7 11.2 8 12.8 9 14.4 Find the value of $\log\left({29517}\right)$ Work: 4+$\log\left({2.9517}\right)$ Thanks for your help

As I posted in another thread, I'm giving the caveat that I am no physicist and have only a rudimentary knowledge of math. Anyway, I am currently reading a book called "Three Roads to Quantum Gravity" by Lee Smolin. I came across a section of the book that confused me. Namely, Dr. Smolin...

Homework Statement I am working on a lab report for a Microwave Optics lab in a Modern Physics class. There is a part in it where I am supposed to derive P_{avg} \propto 1 + cos(δ) . Here is the problem: The electric field of the signal reflected off the fixed mirror can be written as E_1 =...

Hi guys I just want to know why is the current directly proportional to the voltage is that because voltage increase the speed of electrons?? or ,just increase the number of electrons? Thanks in advance

The killing form on a lie algebra is defined as $$B(X,Y) = \text{Tr}ad_X \circ ad_Y$$ where ##ad_X: \mathfrak{g} \to \mathfrak{g}## is given by ##ad_X(Y) = [X,Y]##, where the latter is the lie bracket between X and Y in ##\mathfrak{g}##. Expressed in terms of components on a basis on...

Hi, (I'm not sure if this belongs in the BSM forum...apologies to the moderator if it belongs there.) I'm working through Polchinski's book on string theory (volume 1) and I came cross the definition of the Nambu Goto action. I want to understand why the Nambu Goto action is proportional to...

i want to find V(t) At first i found this problem was very simple but when i try to write differential equations i ended up with these V' = kA that's for sure then i confined the problem only to spherical shape and no other shapes of raindrops involved as i can't express A in term of V alone(...

I'm reading an old article published by Kaluza "On the Unity Problem of Physics" where i encounter an expression for the Ricci tensor given by $$R_{\mu \nu} = \Gamma^\rho_{\ \mu \nu, \rho}$$ where he has used the weak field approximation ##g_{\mu \nu} = \eta_{\mu \nu} + h_{\mu \nu}## where...

Hi guys, This may well be a very trivial question but it isn't immediately obvious to me.. I know if you have x is proportional to y by adding a constant you can say; x = cy However, if we have x is proportional to y + z, is there a similar 'trick' that can be used? Basically, i...

Homework Statement Homework Equations See below The Attempt at a Solution Root Locus? Easy Peasy right? Based on provided equation G(s), i solved the coordinates of the root locus diagram using quadratic equation. For the 2nd part of the question, i have to find gain at which rise time...

I remember learning this in high school, but I can't track down a proof. Let ABC be a triangle and DE a line segment intersecting the triangle such that D is on AB, E is on AC, and DE is parallel to BC. Then...

A lamb grows with its mass proportional to the cube of its length. When the lambs length changes by 15.8% its mass increases by 17.3kg. Find the final mass. Really stumped thanks for any help mf=kxf3 length change by 15.8% xi+.158xi=xf xf=1.158xi mf=k(1.158x)3 mf=1.55kx3 I...

A metal sphere with center at origin has its temperature that is inversely proportional to the position from center. At point P(1,2,2) temperature is found to be 120 degrees What is the rate of temperature change in direction of Q(2,1,3)?

Regarding a potential well that is proportional to -1/|x|, are the amount of possible energy levels finite or infinite? (The potential well is narrow in the middle and approaches a horizontal asymptote as you leave the middle, like the shape of a tornado). I figured it would be infinite...

I has read the link http://physics.stackexchange.com/questions/75411/frequency-of-small-oscillation-of-particle-under-gravity-constrained-to-move-in and, i don't unsderstand why the integral \int^1_0 \frac{dy}{\sqrt{1+y^4}} is proportional to \Gamma (5/4) / \Gamma (3/4) . I had read the...

The M field is the density of induced or permanent magnetic dipole moments. It is analogous to the P field in electrostatics. In electrostatics, the induced P field in a dielectric is proportional to the applied electric field. This is intuitive to me. Why though, in magnetostatics, is the M...

Hi, a long time ago, back in high school, I remember my teacher was explaining the force of gravity to us. He gave us the equation for the force of gravity, which was proportional to the inverse square of the distance. However, he later said that something about Einstein and other researchers...

Homework Statement How does Bernoulli's Equation for calculating the pressure in a moving fluid (as below) explain that drag increases proportionally to the square of the speed? I have been dropping parachutes and recording the time to fall, so my question is in reference to free-fall motion...

acceleration proportional to what?? Hello, We know that according to Hubble's law V=HD that velocity of distant galaxies are proportional to distance from Earth but what about acceleration?? Is acceleration of space with distant galaxies proportional to distance from Earth and one another...

Hi all, When an object is heated , why is the amount of change in its length directly proportional to the original length ? I have read that the increase in length it is directly proportional to the initial length in most of the articles. But I wanted to know how this proportionality arrived...