Second law Definition and 491 Threads

conservation of momnetum or Newtons second law? Homework Statement An acrobat of mass 'm' clings to a rope ladder hanging below a balloon of mass 'M'. the balloon stationary with respect to ground (a) If the acrobat begins to climb the ladder at a speed 'v' (with respect to the ladder), in...

Homework Statement Kepler's second law states that " The line joining the planet and the sun sweeps out equal areas in equal times" Homework Equations Please refer the attachment i have given The Attempt at a Solution Does this mean the area of the triangle on the left is equal to...

Homework Statement This is actually a very elementar Halliday's computational problem: One person pushes a block with a force given by the equation F = 200e^{-0.15t} (given in Newtons and seconds) and the block has, with the surface, a constant friction force of 80N. Find when the block...

Hello no answer is given to this problem so could somebody please tell me if the answer is correct? thanks so much! Two ice skaters, Paul and Tom, are each holding on to opposite ends of the same rope. Each pulls the other toward him. The magnitude of Paul's acceleration is 1.25 times...

Homework Statement This is just a general question. When using Kepler's second law, which radius am I supposed to use to sub into r? Is it the radius of the object (ex. Earth's is 6.38e6 m) or the radius of orbit (ex. Earth's is 1.49e11 m)?Homework Equations C = (GM)/(4pi^2) = (r^3)/(T^2)The...

What I answered is in brackets...what did I answer incorrectly? It is impossible to construct a device that, operating in a cycle, will produce no effect other than the extraction of heat from a reservoir and the performance of an equivalent amount of work. [True] For all naturally...

Spring Force is F = -kx So, because the force is not constant, the acceleration is also not constant.. How then can we apply Newton's second law: F = mass x acceleration to springs?

So if you've seen/posted in any of my other threads you probably noticed that I've been trying to figure out how the modern form of Newton's Second Law (\textit{F = ma} or \textit{F = m}\frac{dv}{dt}) came to be formulated. After reading many different websites and sources, I think I've...

as much i know second law of thermodynamics states that in any closed system the entropy of system always increases(from order to disorder) can any closed system go from order to disorder without interacting to it's surrounding? if it can't...then the system will never b closed or the second...

I don't get how this ever came to be a law, since it seems so obviously false. Entropy in a closed system can only increase. If I close the doors in my room (so that it's a closed system) and spend one hour cleaning, then I have obviously decreased the entropy. It seems so obvious to me that...

can someone give me an example of isolated open systems ,which can allow me to understand 2nd law of thermodynamics?,bcoz i don't think there's anything called open system and that too in isolation

Homework Statement a mass of 10kg, initially at rest, is acted on by a force of 10N for 10 s. What is the final velocity of the mass? Homework Equations i think this equation should help: F= change in momentum/ time The Attempt at a Solution hey everyone i am out of school so...

Homework Statement Okay, so here's the question: Does your plot of acceleration versus hanging mass verify the Second Law? Explain your answer. The experiment involved a cart with weights and a hanging mass on the edge of a table. After each trial, one weight was removed from the cart...

Newton's second law states F = d(mv)/dt as this law is valid only for constant mass systems it is also written as F = md(v)/dt. But let's suppose the mass was not a constant, then the derivative of the law would become F = m'v + mv' (where by ' I mean derivative, m' = dm/dt), would that be...

Hi, A heat engine operates between a high-temperature source and a sink at a lower temperature as shown below: The diagram shows a hot reservoir transferring energy to a engine that does work and dissipates the remaining energy into a cold sink. The question is: There is a gain in...

Homework Statement http://img104.herosh.com/2011/05/20/237027318.jpg Homework Equations F=ma The Attempt at a Solution i got 8.66x10^-17 and 3.9x10^-67 Please i need help.

Which formulation of Newton's second law is more fundamental?? Hi there! I was Googling for interesting demonstrations in Physics, and I was lucky enough to find very interesting blog. Although it is completely new- the guy is writing it only for two weeks, but it already has a lot of nice...

Newton's Second Law...Incline (constant accel) Homework Statement Given: mass of block of 5.0 kg incline angle is 37theta coeff kinetic friction is 0.50 What is the force, directed up the inline, required to move the block at constant speed up the incline? The...

Homework Statement A drop of water of mass m is falling vertically towards the ground. Due to moisture, the mass of the drop is increasing as given by m=kt2. The equation of motion is mdv/dt + vdm/dt = mg find v after 1 second.Homework Equations The integrating factor of an imperfect...

Is Newton's second law somewhat "arbitrary" I am trying to undestand something basic here. Newton formulated his second law as: The rate of change of momentum of an object equals the force acting on it in (considering througout this discussion only intertial frames to keep things simple)...

?Use Newton’s second law F = ma to prove this equation Homework Statement [PLAIN]http://img834.imageshack.us/img834/338/2010b6.gif Homework Equations Can somone show me the proof i don't no anything about this, any websites which tell u how to do questions like these. Is there any...

Does Newton‘s second law hold true for an observer in a car as it speeds up, slows down or rounds a corner?

A reversible engine works between three thermal reservoirs-A,B and C.The engine absorbs an equal amount of heat from the thermal reservoirs A & B kept at temperatures Ta and Tb respectively,and rejects heat to the thermal reservoir C kept at temperature Tc.The efficiency of the engine is\alpha...

A reversible engine works between three thermal reservoirs-A,B and C.The engine absorbs an equal amount of heat from the thermal reservoirs A & B kept at temperatures Ta and Tb respectively,and rejects heat to the thermal reservoir C kept at temperature Tc.The efficiency of the engine is \alpha...

Hi all, first post so be nice :) I'm currently taking a statistical physics course and I am very confused about an aspect relating to the second law. Currently we are considering a member of an ensemble to be represented by a moving point in phase space (a 6N dimensional space spanned by...

Homework Statement An object is dropped from a height above a pool of water. Start with Newton’s 2nd law, F = ma and use the general expression for acceleration, ay=d2y/dt2 to generate a differential equation Homework Equations F=ma -mg=m d2y/dt2 The Attempt at a Solution We had this...

A block sits on a horizontal frictionless table. A thread attached to its runs horizontally to a pulley at the edge of the table, passes over the pulley and supports a load of 1.0 kg. The size of the acceleration of both the block and the load is 2.0 m/s. Find the tension in the thread: To...

So I had this problem regarding an elevator with a man inside. In the first part of the question we had to calculate the tension in the cable, which I managed to do alright. The Second Part however, I am having difficulty and it asks for the following: When the lift is decelerating by 1...

Hi, all. A while ago, I was told of an experiment where the Second Law of Thermodynamics was violated. The experiment involved mirrors or some other sort of optical devices to "move around" some particles, and upon moving these around, the entropy of the universe decreases. I was wondering...

In order for decoherence to work, does it require the second law of thermodynamics to be valid?

What is the "real" second law of thermodynamics? Title says it all.

Homework Statement Suppose a can of soda is sitting out in a room that has a temperature of 73 degrees. The temperature of the soda itself is 50 degrees. How long will it take for the soda to warm up to the temperature of the room? The Attempt at a Solution I know what I can do is...

Of course, the second law of thermodynamics implies that all closed systems will go from a state of state of order to disorder. Chaos theory offers the possibility of systems developing patterns and order from seemingly disordered or chaotic systems. Do these theories contradict or is there...

Homework Statement Imagine a narrow pipe, filled with fluid, in which the concentration of a certain type of molecule varies only along the length of the pipe (in the x direction). By considering the flux of these particles from both directions into a short segment \Deltax, derive Fick's...

Homework Statement Two masses, m1 = 3.50kg and m2 = 5.00 kg, are on a frictionless tabletop and mass m3 = 7.60kg is hanging from m1. THE COEFFICIENT OF STATIC AND KINETIC FRICTION BETWEEN m1 AND m2 are 0.60 and 0.50 respectively. a) What are the acceleration of m1 and m2? Homework Equations...

Homework Statement Boxes A and B are at rest on a conveyor belt that is initially at rest. The belt is suddenly started in an upward direction so that slipping occurs between the belt and the boxes. Knowing that the coefficients of kinetic friction between the belt and the boxes are (\muk)A =...

Can you please tell me were I am wrong? I define the entropy (as usual) as S[\rho] = -k_B \text{tr}(\rho\ln\rho) The time development of the density operator is \rho(t) = U(t)\rho(0) U^\dagger(t) That means S[\rho(t)] = S[U(t)\rho(0) U^\dagger(t)] = S[\rho(0)] where I used...

Homework Statement Suppose that during the launch of a rocket from the surface of the earth, an astronaut onboard the rocket stands on a bathroom scale and measures her weight to be 3.6 times her normal weight. Determine the acceleration of the rocket. Homework Equations Fnet \sumF = ma or...

Homework Statement Hi Say I am given Newtons second law in this form: \frac{{d^2 x}}{{dt^2 }} + \gamma \frac{{dx}}{{dt}} + \omega _0^2 x + const = 0 I know the physical interpretation of all terms except the last one, i.e. the constant. Does this go into the restoring-force term...

Homework Statement A balloon containing 2.00 x10^3 m3 of helium gas at 1.00 atm and a temperature of 15.0°C rises rapidly from ground level to an altitude at which the atmospheric pressure is only 0.900 atm. Assume the helium behaves like an ideal gas and the balloon's ascent is too rapid to...

Hello there! Could someone please help me with setting the starting equations for coupled oscillators. I'm having serious troubles with setting the +- signes right (yes, more than with the differental equations :) ). OFF TOPIC: any reading materials about problems with signs in physics will...

Homework Statement An object of mass m_1 hangs from a string that passes over a very light fixed pulley P_1. the string connects to a second very light pulley P_2. A second string pases around this pulley with one end attached to a wall and the other to an object of mass m_2 on a...

Homework Statement Use the first DeMorgan's law and the double negation law to derive the second DeMorgan's Law Homework Equations First DeMorgan's law is - (P and Q) is equivalent to - P or - Q Negation Law is - - P is equivalent to P Second...

A student stands on a bathroom scale in an elevator at rest on the 64th floor of a building. The scale reads 836 N. (a) As the elevator moves up, the scale reading increases to 936 N, then decreases back to 836 N. Find the acceleration of the elevator (ms^-2). (b) As the elevator approaches...

Newton's Second law of motion F=ma, where m is the mass of the object that undergoes an acceleration a due to to an applied force F. This law is accurate at low speeds. At high speeds, we use the corresponding formula from Einstein's theory of relativity...

Homework Statement 2. Question 3 The Attempt at a Solution I would like to state the fact that friction during the lab was not taken account of however I do not understand how that ties into question number three... Is it because the graph is based on a theoretical value which is...

How did Kepler figure out his second law: Equal area in equal time?

Homework Statement In figure (a), a 5.4 kg dog stands on a 16 kg flatboat at distance D = 6.1 m from the shore. It walks 2.1 m along the boat toward shore and then stops. Assuming no friction between the boat and the water, find how far the dog is then from the shore. Homework...

Homework Statement The only force acting on a 4.3 kg body as it moves along the positive x-axis has an x component Fx = -8x N, where x is in meters. The velocity of the body at x = 1.6 m is 11 m/s. (a) What is the velocity of the body at x = 4.5 m? (b) At what positive value of x will the body...

Forces of 10.6 N north, 20.8 N east, and 14.3 N south are simultaneously applied to a 3.76 kg mass as it rests on an air table. What is the magnitude of its acceleration? I tried F=√(10.6²+20.8²) a=F/m ..however this is incorrect. Can someone please tell me where I am going wrong?