Second law Definition and 479 Threads

Homework Statement I'm taking a test next week on kinetics and energy of moving particles. Problems include things like sliding blocks, friction, braking automobiles, collars sliding on poles, springs, max/min heights/velocities, tensions, accelerations, etc... We learned two ways of...

Deriving Vr and V(sub-theta) from Kepler's second law and... Homework Statement Beginning with r=[a(1-e2)]/(1+e*cos \theta) and Kepler's second law, derive general expressions for vr and v\theta for a mass m1 in an elliptical orbit about a second mass m2. The final answers should be...

Homework Statement Two objects A and B, with masses m1=1.00kg and m2=2.00kg, are connected with an ideal string. Object A is moving on an ideal incline with 0 friction. Object B is moving vertically. A force F is working on object B. Its magnitude is 6.00N. Object b is accelerating downward...

Homework Statement A spaceship lifts off vertically from the Moon, where g = 1.6 m/s2. If the ship has an upward acceleration of 1.0 m/s2 as it lifts off, what is the magnitude of the force exerted by the ship on its pilot, who weighs 735 N on Earth? From Halliday, Fundamentals of Physics...

Homework Statement This is a basic conceptual question that i encountered when i was reading the section on Entropy on the book by K. Huang on statistical mechanics, it goes like this. In a reversible isothermal expansion of an ideal gas, i know that the change in internal energy is zero...

In my thermodynamics book it states that the first law is, " When a system undergoes a complete cycle the net heat supplied plus the net work input is zero" And then it states that for the second law, "In any complete cycle the gross heat supplied plus the net work input must be greater...

hello! here's my problem: Newtons second law implies: F=m*dv/dt+v*dm/dt first part of the equation says if I act on the object then it's reaction will be acceleration, but the second part says if act on the object it will cause changes in object's mass. In case where I'm dealing with non...

In my opinion the nature of the second law of thermodynamic is probabilistic and it sholud be formulated in a way which determine probability that given proces occurs (the probability should depened on the tatal entropy change, if its negative the proces is very unlikely but in principle...

One of the most classical and verified principles of physics is that entropy never decreases. E.g. gas occupying half of a 1L container will quickly disperse quite-evenly throughout the container. It seems however, that QM easily allows momentary violations of this principle. For instance...

Homework Statement A cyclist and her bicycle have mass 75kg. she is riding on a horizontal road, and positions herself so that 60% of the normal contact force is on the back wheel and 40% on the front wheel. The coefficient of friction between the tires and the road is 0.8. What is the...

I read in the paper that the 2nd law of thermodynamics says energy is constantly decreasing in a closed system. Is that true? I learned the law in my first year of college but I can't remember its implications. Anyway, I can't find a straight 'true' or 'false' answer anywhere, and it's...

Hi All, The basis of Kirchhoff's second law is that an electric potential function is well defined, in such a way that, in a closed path, the potential difference between initial and final points (the same point) will be zero. However, when we introduce in the circuit an inductor, we...

Homework Statement How can Newton's 2nd law be derived for a single body in an 1Dimesional case ? Homework Equations F=m(du/dt) The Attempt at a Solution It is given that the principle of conservation of energy must be used,for the derivation. Are there any more hints?

Homework Statement A box is being pulled up a ramp with a force F. The ramp has a 30 degree incline with the horizontal. write the sum of the forces in the x direction and y direction. Make the x and y coordinate system be parallel and perpendicular with the ramp. The Attempt at a...

WCFSGS' Version: Generalized Second Law of Thermodynamics We have known that there has been some generalization to the second law of thermodynamics. We like to present here the Version of WCFSGS about this generalization. At this moment, we are not quite sure if our version is different from...

So i have the equation m*(d2x/dt^2)+c*(dx/dt)+kx=0, where d2x/dt^2 is the second derivative. So I'm given that m=10 kg, and k=28 N/m. At time t=0 the mass is displaced to x=.18m and then released from rest. I need to derive an expression for the displacement x and the velocity v of the...

Homework Statement Show that the second law of thermodynamics predicts the spontaneous freezing of liquid water at -5^{o}C under 1 bar of constant pressure. Assume that Cp is temperature independent. Standard water fusion enthalpy = 6.008 kJ/mol @ 273.15 K \geq has to be interpreted as...

Homework Statement In the tropics, the water near the surface is warmer than the deep water. Would an engine operates between these two surfaces violates the second law? Why? Homework Equations Clausius statement: Heat generally cannot flow spontaneously from a material at lower...

Homework Statement A cable is used to suspend a 400 kg safe. It is being lowered at 6 m/s, when it stops suddenly. Find the maximum dynamic tension and the frequency of vibration. k=2(105 N/m Homework Equations Newton's 2nd law The Attempt at a Solution Well I easily found the...

Homework Statement A car pulls a trailer along a level road at a steady speed of 10 m/s and the pull on the trailer is 100N. When the car accelerates at 0.5 m/s2 the pull on the trailer is 150N. Assuming the resistance to motion to be constant, find the mass of the trailer. Homework...

from the second law of Newton we know... applied force is proportional to the change of momentum...that means F= k( mv-mu) where k is constant ...from here now proof F=ma

What is the explanation behind this law? I've read tons of definitions for it and I still can't understand it. Will you please also provide examples for it?

Homework Statement 4. A particle of mass m is experiences a Force that attracts the particle following F(x) = -k*x^-2 (an inverse square relationship) where x is the distance from an origin at x = 0 and k is a positive constant. If the particle is released from rest at x = d, how long...

Homework Statement the rotor blades of a helicopter propel 2500 kg of air vertically downwards every second. The air, initially at rest, is accelerated to a speed of 15 ms-1. If the helicopter starts to rise with an acceleration of 12.5 ms-2, the mass of the helicopter is... a. 1680 kg...

So if F=Ma then if there was no accleration but it was going at constant velocity there would still be force right? but what? and how

SOLVED (Problem 10, Chapter 2, Modern Physics - Serway) Homework Statement Recall that the magnetic force on a charge q moving with velocity \vec{v} in a magnetic field \vec{B} is equal to q\vec{v}\times\vec{B}. If a charged particle moves in a circular orbit with a fixed speed v in the...

Please explain.

18. An elevator that weighs 3.5 x 103 N is accelerated upward at 1.0 m/s2. What force does the cable exert to give it this acceleration? A. 357 N B. 0 N C. 3500 N D. 3857 N (For this quesion I was really confused and I guessed that the force of tension in the cable was what the cable...

Homework Statement I have to prove that A1=A2, or the fact that planets will sweep out equal areas in equal amounts of time. The planet I have to do this for is Pluto. Basically, I need help finding the area it "sweeps out" over any length of time of my choosing. Homework Equations...

If a force is applied to an object, will the object always experience the same linear momentum change regardless of where the force is applied, or will applying the force away from the objects centre of mass cause lesser linear momentum to develop but with the addition of angular momentum...

Says, in a closed system disorder is always increasing, more or less. But with gravitational forces, matters are sticking together--creating order. Thus the law=invalid Can I get my Noble?

I am curious about the how Newton discovered his laws of motion and his law of universal gravitation. It seems in modern education, the laws are introduced to students somewhat 'magically', and then the students then do various practical experiments and calculations to verify them. If we step...

Second Law of Thermodynamics - Postulate or Provable?? I know that the 2nd law of thermodynamics is considered an experimental fact, but I have yet to find any sort of structure when I see a discussion of the law via proving it as a theorem. I know there are mathematical formulas that express...

Homework Statement Premium gasoline produces 1.23×108 J of heat per gallon when it is burned at a temperature of approximately 400 ºC (although the amount can vary with the fuel mixture). If the car's engine is 25.0 % efficient, three-fourths of that heat is expelled into the air, typically...

the proof of second law of Newton for rotation goes like this: take a sphere rotating around some far axis FT=maT FT=m * ALPHA * R multiple by R tau = mR2 * ALPHA and we can say it true for every limit mass in a body. so sigma tau = sigma (mR2) * ALPHA sigma tau = I * ALPHA...

Homework Statement Stopping a Salmon The tension at which a fishing line snaps is commonly called the line's "strength." What minimum strength is needed for a line that is to stop a salmon of weight 85 N in 11.6 cm if the fish is initially drifting at 3.0 m/s? Assume a constant acceleration...

Homework Statement Block A weighs 1.14 and block B weighs 3.66. Block A rests on top of block B and has a cable connecting it to the wall on its right. The coefficient of kinetic friction between all surfaces is 0.300. Find the magnitude of the horizontal force necessary to drag block B to...

Homework Statement A particle is traveling in a straight line at a constant speed of 22.1 m/s. Suddenly, a constant force of 12.6 N acts on it, bringing it to a stop in a distance of 55.3 m. Homework Equations The Attempt at a Solution (a) What is the direction of the force...

Homework Statement I've been given a problem that an object falls from a distance of 800 feet with an initial velocity of 4 f/s. Gravity acts on the object, but air resistance can be disregarded. Find the location at time t and find when the object hits the ground. The Attempt at a...

[SOLVED] W=Fd, Work & Newton's Second Law problem Homework Statement a) Find the force to give a helicopter of mass M an acceleration of 0.10g upward b) Find the work done by this force as the helicopter moves a distance of h upward. Homework Equations W=F_{net}d F=ma The Attempt...

Is conservation laws are more fundamental than Newton's second law in Newtonian mechanics? I know from the point of view of Noether's theorem conservation laws are more fundamental. But all the conservation laws can be derived from the F= ma equation. And from these conservation laws I can't...

Homework Statement "Given F=dp/dt. If the force is parallel to velocity show that F=γ3ma." Homework Equations F=dp/dt and p=γmv The Attempt at a Solution Since the force is the first derivative of the momentum with respect to time, and γ and v both vary with time since there is a...

When a 53.4g tennis ball is served, it accelerates from rest to a speed of 40.5m/s. The impact with the racket gives the ball a constant acceleration over a distancce of 46.6cm. What is the mgnitude of the net force acting on the ball? I converted the 53.5g into kg=.0535kg I converted 46.6cm...

Newton's second law problem; Please Help! Block M = 7.50 kg is initially moving up the incline and is increasing speed with a = 4.35 m/s2. The applied force F is horizontal. The coefficients of friction between the block and incline are fs = 0:443 and fk = 0:312. The angle of the incline is...

Homework Statement A person jumps from the roof of a house 4.4 m high. When he strikes the ground below, he bends his knees so that his torso decelerates over an approximate distance of 0.70 m. The mass of his torso (excluding legs) is 40 kg. (a) Find his velocity just before his feet...

Homework Statement Consider all possible isothermal contractions of an ideal gas. The change in entropy of the gas: A) does not increase for any of them B) increases for all of them C) is zero for all of them D) decreases for all of them E) does not decrease for any of them...

Homework Statement A sphere of mass 1.1 × 10^-4 kg is suspended from a cord. A steady horizontal breeze pushes the sphere so that the cord makes a constant angle of 23° with the vertical. Find (a) the magnitude of that push and (b) the tension in the cord. Homework Equations F_g = m*g F_net...

second law of thermodynamics and black holes ?! I am having a hard time thinking about the perservation of the second law of thermodynamics in black holes. If we throw a mass that have some level of disorder (entropy) into a black hole, it will disappear and that will appear to us as violating...

In the amusement park ride known as Magic Mountain Superman, powerful magnets accelerate a car and its riders from rest to 42 m/s (around 90 mi/h) in a time of 8.1 s. The mass of the car and riders is 4800 kg. Find the average net force exerted on the car and riders by the magnets. my...

Homework Statement Two blocks with masses m1 = 1.10 kg and m2 = 3.20 kg are connected by a massless string. They are released from rest. The coefficient of kinetic friction between the upper block and the surface is 0.490. Assume that the pulley has a negligible mass and is frictionless, and...