2nd law Definition and 292 Threads

this is going to be a newbie question... i couldn't understand why a system in thermodynamic equilibrium must with maximum entropy? and this is just 100% sure that within an isolated system entropy never decreases? thank you in advance for your reply...

Homework Statement a heavy object of mass m is suspened in a room through a linear spring whose spring constant is k. Initially the object is suspported so that the spring is at its free length (neither strecthed/compressed) which is take to be x=0. At time zero the support is removed and...

I have a question pertaining to the motion of the center of mass (CM) of several connected bodies. Homework Statement Here is a picture of the set-up (green surfaces are stationary): The mass of the spring is zero. The mass of the disk is M1. The mass of the bar is M2. There is a pin...

Robert Braeunig has an great blog on rocket science here: http://www.braeunig.us/space/index.htm, and I've been trying to follow the math his piece on Orbital Mechanics. I'm having trouble in particular following his description on Kepler's 2nd law, here's how he puts it: Figure 4.5...

Homework Statement As an application of TD and to demonstrate the power of the formalism of differential forms, show that if one defines the ideal gas temperature TI (T) from the ideal gas equation p V = N KB TI(T); this is related to the absolute temperature T (from the second law) by TI...

The problem is: In the figure here three ballot boxes are connected by cords, one of which wraps over a pulley having negligible friction on its axle and negligible mass. The masses are mA = 31 kg, mB = 40 kg, and mC = 13 kg. When the assembly is released from rest, (a) what is the tension in...

First of all I'm not sure if this is the right forum for this problem. Homework Statement Given that \overline{F}=m\overline{a} is valid in the lab frame S, show that: (a) it is also valid in a moving frame S' with a constant velocity relative to S, but (b) invalid in a moving frame with...

I haven't taken a physics course in years so I am little lost. A ball is thrown with initial speed $v_0$ up an inclined plane. The plane is inclined at an angle $\phi$ above the horizontal, and the ball's initial velocity is at an angle $\theta$ above the plane. Choose axes with $x$ measured...

1. "A 40.0-kg crate is pulled along a horizontal floor by the ideal arrangement shown in figure below. The force F is 280 N. The coefficient of kinetic friction between the crate and the floor is 0.170. What is the acceleration of the crate?" ______box---^=Pulley__ Okay, this is a...

Homework Statement http://www.diigo.com/item/image/2sb3i/ahcq Homework Equations Ʃ\vec{F} = m\vec{a} The Attempt at a Solution For M : T - mg = ma T - 19.6 = 2a (1) For 2M : 40 cos (150) - T = 4a from (1) : T = 2a + 19.6 substituting : 40 cos (150) - (2a +19.6) = 4a 40 cos (150) - 19.6...

I've attached an image explaining the problem. All pulleys are massless. Basically, they want me to show some relations between wire tensions, using Newtons 2nd law for rotational motion. This law is written in my book as: dL / dt = torque, where L is angular momentum. I'm not sure...

A 2.5 kg mass accelerates at 6.1 m/s in adirection 37◦north of east. One of the two forces acting on the mass has a magnitude of 6.05 N and is directed north. Determine the magnitude of the second force. Answer in units of N I know you have to break it up into multiple components, but otherwise...

A Person in "Free Fall" Newton's 2nd Law Homework Statement An 80kg aviator is in free fall and acquires a velocity of 60 m/s and then opens his parachute. After falling an additional 30m, his velocity has been reduced to 20 m/s. What is the average acceleration of the aviator while his fall...

If an isolated body starts to accelerate, why would saying the system isn't properly isolated render Newton's second law meaningless? pg. 60 of K&K...

Homework Statement A dockworker applies a constant horizontal force of 80 N to a block of ice on a smooth horizontal floor. The fritional force is negligible. The block starts from rest and moves 11 meter in 5 seconds. What is the mass of the block of ice? Homework Equations Newton's...

Homework Statement We did a lab in class where we had a cart and we had nothing on top of it. We added different forces at the end of a pulley to see how the acceleration differed with different forces. One of the questions on our lab was: We tried to keep the "mass constant". Why is this...

Hi, everyone ! I am a new member to PF but I find it helpful as people will give ideas and suggestions for me :) Recently,I come across something called as a magnetic motor. From the design, a few permanent magnets are placed on the edge of a circular disk. Then, as another magnet approaches...

Is shown like this in my book: Consider a rotating body with an angular acceleration α. There must be a tangential force component if it is rotating: For a general point on the body we can write: Ftan = mi * ai = mi * ri * α (1) Multiply by ri and sum up you...

A car of mass 1000 kg tows a caravan of mass 600kg up a road which rises 1m vertically for every 20m its length. There are constant frictional forces of 200N and 100N to the motion of the car and caravan respectively. the combination has an acceleration of 1.2ms-2 with the engine exerting a...

rate of change of momentum. Newton 2nd law (solved) hailstones with an average mass of 4grams fall vertically and strike a flat roof at 12ms-1 . In a period of 5 minutes, 6 000 hailstones fall on each square meter of roof and rebound vertically at 3ms-1 . Calculate the force on the roof if it...

Hello all. As I'm a newbie here please excuse any misconceptions in my following question concerning the 2nd law of thermodynamics and heat/energy flows. Although energy will not spontaneously flow from a colder to a warmer object - the colder object still emits IR photons toward the...

I'm just curious about the second law. I was taught in secondary school that the definition of the 2nd law was just when a resultant force acts on an object with a constant mass, the object will accelerate and move in the direction of the resultant force. The product of the mass and the...

I ve read that according to 2nd law,in a closed system where there's no inflow and outflow of energy,the potential energy of such system continuously decreases... So where does/ what is this energy converted to.?

( part a only I don't understand how you know from this question that it is a constant pressure process. I thought it is a polytropic process. So it will have a pVγ curve. I was drawing a pV curve. The answer is a straight line parallel to x- axis. My question: How do I know from...

Homework Statement Define the second law of thermodynamics in two different ways and show these two ways are equivalent. Homework Equations The Attempt at a Solution Could anyone give me any pointers as to what this might mean? I know what the 2nd law of thermodynamics states...

Homework Statement In the figure http://i.imgur.com/Y5Vc7.gif shows a uniform disk (M = 2.5kg, R = 0.20 m) mounted on a fixed horizontal axle. A block (m = 1.2kg) hangs from a massless cord that is wrapped around the rim of the disk. The cord does not slip and there is no friction. Find the...

I don't have the intuitive picture of thermodynamic 2nd law, in terms of statistical mechanics. That is, why should the number of microstates be maximized in equilibrium? Anyone gives an intuitive explanation? Thanks a lot.

hi, thank you for any help. -[problem understanding angular momentum and Newton (second)2nd law] -[usual/classic problem of spinning bike wheel on rope doesn't fall] (from 28min:10s to 29min:15s and also 37:48 to 39:00)...

Homework Statement A car travels on a horizontal street, straightforward. In some moment of time (t = 0), having a velocity of 20 m/s, the break is hit. It is required to find the time and traveled distance before the car is still standing. The friction coefficient between the wheels and the...

Homework Statement I attached the photo of the question that has everything. Homework Equations F=ma The Attempt at a Solution So I found the total mass of the system 50+35 = 85. Since we are given the force in the x-direction I used \frac{70}{85} = a = .8235 . The weight of...

Consider a thermodynamic system of two independent variables, like a gas inside a recipient, at equilibrium. We are now going to carry out two different transformations at constant volume: Transformation 1) A reversible process where an amount of heat Q is "given" to the system...

By the end of the day, I must admit that the rotational analog of Newtons 2nd law: Τ = I*α contradicts my intuition. Suppose that you take a part of a body in the radius r from the rotational axis and exert a force on that. It will then get a linear acceleration. We can then find the angular...

"Newton 2nd Law" word problem help Homework Statement When the click beetle jumps in the air, its acceleration upward can be as large as 400.0 times the acceleration due to gravity. (An acceleration this large would instantly kill any human being.) For a beetle whose mass is 40.00 mg...

【Atwood Machine Problem】 Homework Statement Regular atwood machine lab where you test the proportionality of net force and acceleration as stated in Newton's 2nd Law. The regular lab procedure is to release the smaller mass at rest, to let it be lifted by the heavier one. Question is: "How...

Hey guys, how would I show that a = g sin(alpha) for the following diagram?

This morning while riding my motorcycle, a black bird smashed into my helmet. Considering a black bird weighs approx. 80-120 gram (according to google), I was surprised by the force of the impact. Anyways, now I'm wondering if anyone could calculate with what force the bird hit the helmet...

Homework Statement A lightweight string of length 60.0 cm is attached to the ceiling at points separated by distance D, as shown on the diagram in my attachment. Three objects of equal mass are hung from the string, separating the string into four equal segments of lenth L. If θ=40° , find...

Homework Statement Question: A 3.45 kg object is attached to a vertical rod by two strings as in Figure P6.11. The object rotates in a horizontal circle at constant speed 5.65 m/s. What are the tensions of the two strings, individually? Variables: m = 3.45kg length of both strings...

hello all Consider an experiment to prove that the acceleration in a certain direction on a given mass is directly proportional to the resultant force in that direction given that the given mass is constant. The acceleration can be measured using light gates. This resultant force can be...

Second Law of Thermodynamics says that "it is impossible to extract an amount of heat QH from a hot reservoir and use it all to do work W" "Some amount of heat QC must be exhausted to a cold reservoir. " my questions is... why?

In Figure 5-51a, a constant horizontal force a is applied to block A, which pushes against block B with a 20.0 N force directed horizontally to the right. In Figure 5-51b, the same force is applied to block B; now block A pushes on block B with a 10.0 N force directed horizontally to the left...

Homework Statement http://rwdacad01.slcc.edu/academics/dept/physics/tvanausdal/2210/problems/force/force3.htm A block is given a push up the incline so it has an initial velocity of 5 m/s up the incline. If the incline angle is 30 degrees and the coefficient of kinetic friction is 0.2...

A body of mass m (kg) is falling vertically under gravity g m/s2 in a medium whose resistance to the speed of the body, v m/s, is proportional to vn (n positive). If the body was released from rest and has terminal velocity, vt m/s, use Newton's 2nd law of motion to show that its...

it is often stated that time travel is not forbidden by any law of physics. but doesn’t the second law of thermodynamics forbid it because going back in time would involve a decrease in entropy?

A satellite of mass m is in Keplerian orbit around a parent body of mass M >>m. The satellite has total energy E and angular momentum l, where angular momentum is measured about the parent body and the zero of potential energy is at infinity. Determine the semimajor axis a and the eccentricity e...

In the first part of Brian Cox's documentary series 'Wonders of the Universe', he explains how the entropy of the universe always increases, and that we are therefore headed for a state of total 'disorder' where all is left of the universe is photons and dying black holes. But wasn't this...

After reading the 2nd law of thermodynamics and entropy, it let's me think about our building. since entropy tends to maximize as time flows, doesn't that our building will slowly tends to collapse as our building has such low entropy at first? how can we measure such rate? or does can the...

Is it fair to say that the 2nd Law basically is the law of large numbers, which given the immense numbers of microstates involved in entropy calculations, is inviolable? With a Boltzmann distribution, one could have arbitrarily small decreases in entropy from time t to t+1 as for a system...

Hi, I'm having trouble with these problems dealing with Newton's 2nd Law 1] Two blocks are in contact on a frictionless table. A horizontal force is applied to the larger block, as shown in Fig. 5-50. (a) If m1 = 2.0 kg, m2 = 1.4 kg, and F = 2.7 N, find the magnitude of the force between the...

If you look at Earth 3000 years ago versus the Earth today there is now far more structure, ie cities, roads etc. It is less random, it has less entropy, and that is as a result of life. Especially intelligent life. Considering the solar system as a whole, does the decrease in entropy...