What is Second law: Definition and 491 Discussions
The second law of thermodynamics establishes the concept of entropy as a physical property of a thermodynamic system. Entropy predicts the direction of spontaneous processes, and determines whether they are irreversible or impossible, despite obeying the requirement of conservation of energy, which is established in the first law of thermodynamics. The second law may be formulated by the observation that the entropy of isolated systems left to spontaneous evolution cannot decrease, as they always arrive at a state of thermodynamic equilibrium, where the entropy is highest. If all processes in the system are reversible, the entropy is constant. An increase in entropy accounts for the irreversibility of natural processes, often referred to in the concept of the arrow of time.Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory. Statistical mechanics provides a microscopic explanation of the law in terms of probability distributions of the states of large assemblies of atoms or molecules. The second law has been expressed in many ways. Its first formulation, which preceded the proper definition of entropy and was based on caloric theory, is Carnot's theorem, credited to the French scientist Sadi Carnot, who in 1824 showed that the efficiency of conversion of heat to work in a heat engine has an upper limit. The first rigorous definition of the second law based on the concept of entropy came from German scientist Rudolph Clausius in the 1850s including his statement that heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.
The second law of thermodynamics can also be used to define the concept of thermodynamic temperature, but this is usually delegated to the zeroth law of thermodynamics.
Hello everyone,
These days i am studying thermal physics in my classes so had a few queries to get clear about.
The Kelvin statement says:
“ No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. ”
Yet the...
I'm curious how to solve Fick's second law of diffusion \frac{∂c}{∂t}=D \frac{∂^2c}{∂x^2}For conditions:c(x,0)=0c(0,t)=Ac(\infty,t)=0Physically this means:
-c(x,t) is the concentration at point x at time t.
-Initially there is no concentration of diffusing species.
-At x=0 for all t the is a...
A car of mass 1200 kg is started from rest and pulled on the level ground by an engine. The resistance of the motion is Kv, where v(m/s) is the velocity of the car at time t(s). The power of the engine is constant and equal to 80000 watts.
a) How does P, the power of the engine connect to F...
Homework Statement
A certain force gives object m1 an acceleration of 12.0 m/s2. The same force gives object m2 an acceleration of 3.30 m/s2. What acceleration would the force give to an object whose mass is (a) the difference between m1 and m2 and (b) the sum of m1 and m2.
Homework...
Homework Statement
Question is here http://postimage.org/image/som50onyv/
Homework Equations
F=MA
The Attempt at a Solution
for a) Power = force * speed
for b) Force = Mass * Acceleration
F = m * dv/dt
for c) for maximum velocity, there must be zero drag
i am...
So this is slightly off topic but still physics related.
I want to get a tattoo of Newton's second law in a few forms on my arm and this is what I've settled on:
\sum{\vec{F}}=\frac{∂\vec{p}}{∂t}=-\nablaφ
The only thing I am a bit worried about, is although I aesthetically like the...
Hi people
Newton's Second Law a=F/m assumes that either a body is pointlike or that force is transmitted instantaneously across it. Special relativity which applies to Newton's First Law and which was developed from the assumption of a finite velocity of energy transmission, has enjoyed...
My question is regarding the reason why the Brownian ratchet fails to negate the second law.
The explanation that I have been told relates to the fact that the molecules in the second chamber would interact with the 'pawl' in a similar manner to those interacting with the paddle wheel...
Homework Statement
If a soccer ball of mass 0.5 kg is kicked with a speed of 14 m/s and hits a rock and is in contact with it for 0.18 seconds, with what force will it hit?Homework Equations
Fnet = ma
The Attempt at a Solution
I have no idea what to do to get the acceleration for the above...
I'm having trouble understanding well what exactly is entropy. I know it involves an irreversible process in a closed system, but for some reason I just can't grasp well the concept.
About the second Law, it involves entropy heavily so I am sure I won't understand it without understanding...
Homework Statement
It's attached.
Homework Equations
F = m*a
F_f = -μ_k*F_N // [Force of friction] = μ_k*[Normal force]
The Attempt at a Solution
So, I think I managed to solve it -- at least, I got what the book got, but I don't understand part of what I did to get the answer...
1)A rock is dropped off a cliff and falls the first half of the distance into the ground in t1 seconds. If it falls the second half of the distance in t2 seconds, what is the value of t2/t1?
Relevant equations: I think the kinematics equations of d=vt+(1/2)at^2
I have no idea how to solve...
1)A rock is dropped off a cliff and falls the first half of the distance into the ground in t1 seconds. If it falls the second half of the distance in t2 seconds, what is the value of t2/t1?
Relevant equations: I think the kinematics equations of d=vt+(1/2)at^2
I have no idea how to solve...
A long time ago when I was in college there was a problem in the back of a chapter on thermodynamics in my freshman chemistry textbook:
A newly designed ship travels the tropical seas by using the warm tropical seawater,converting the heat from the seawater to work, and then expelling ice...
Homework Statement
You are asked to measure the moment of inertia of a large wheel, for rotation about an axis through its center. You measure the diameter of the wheel to be 0.740 m and find that it weighs 280 N (note, that's not the mass!). You mount the wheel, using frictionless...
Homework Statement
• If we add a third block, leaving the 10 N force the
same, what happens to f3,
the net force on the 3 kg
block?
A. Increase
B. Decrease
C. Stay the Same
D. Not Enough Info.
Homework Equations
F net = m * a
The Attempt at a Solution
Ignore the...
Homework Statement
Hello! :)
I got stuck on a problem I got for my physics class, where I am supposed to derive the differential equations for a mechanical system (x'' =, θ'' =, and φ'' =) , and then simulate how the system behaves in matlab.
Here is a picture...
Homework Statement
Hi
In a book they state
\frac{dv}{dt} = a \quad \Rightarrow \quad v(z) = \sqrt{2a(z-z_{max})}
I am trying to reproduce this. Here is what I have so far:
dv/dt = (dv/dz)(dz/dt) = v(dv/dz) = a
Since a is constant (I assume?), I get
\int vdv = \int adz \quad...
I am interested in finding as many unit less representations of the second law of thermodynamics as possible. other then gravity, it is the physical law that we experience most in daily life. to greater or lesser extents it can used to describe everything that controls our existence. I'm looking...
Homework Statement
An astronaut is taking a space walk near the shuttle when her safety tether breaks. What should the astronaut do to get back to the shuttle?
Attempt to "swim" toward the shuttle.
Take slow steps toward the shuttle.
Take a tool from her tool belt and throw it away...
Homework Statement
http://imageshack.us/photo/my-images/534/jillo.jpg/
Okay, so I was given a diagram that looks like the one I linked to above.
This is pretty basic, using Newton's second law to find-
A) the weight of the "lamp"
B) the tension in the chain
The strut is exerting a...
physics help please...
a person with a mas of 75.0 kg is wearing roller blades and stands at rest on top of a long hill. the hill makes an angle of 15.0 above horizontal. assume the coefficient of friction to be .10.
a. determine the acceleration of a the person as they roll down the...
Homework Statement
Thanks for looking. My understanding of Newton's Second Law, F=MA, is: If I give some mass a force, it will accelerate at some rate.
Imagine an infinite, frictionless surface. If I give a box of 1kg a push of 6 Newtons, it will accelerate at 6 m/sec2. So, at t=0, v=0. at...
I need a clarification about the reversibility criteria in classical thermodynamics.There are two criteria in it to my understanding.one is that there should be no dissipative forces i.e no friction.The second is that there is no heat flow across a definite temperature gap--only across an...
People say that Newton's Second law is the real Law of Motion because both the First and the third law can be proved from the second. If this is true why did Newton state them as separate laws if they are just special cases of the 2nd law? My teacher taught us this.
These are the proofs she...
Homework Statement
Hello guys. Really need your helps. When I construct an equation(moment about point O), do I have to include the rod's mass also? I've heard that I can neglect the rod's mass due to equilibrium equation. On the other hand, I've also heard that I can only neglect mass if the...
As far as I know, you can't prove laws, but anyway...
We got to do an experiment at school. A weight is suspended vertically from a string which is connected to a trolley which is placed horizontally on a flat table. There's a pulley at the edge of the table to reduce friction. Then we let...
I would like to know if 100 watts of electricity can boil a liter of water over time. If the vessel containing the water is insulated say with arogel insulation or a partial vacuum. The reason for asking this question, in the second law of thermodynamics it says that "heat goes from a region of...
Are there any cases in Newtonian physics where it is valid to apply Newton's second law in the form ƩF = m dv/dt + v dm/dt, in which dm/dt is non-zero?
It is my belief that there are no such cases. For example, if one applies momentum conservation to a rocket in a field-free region, we obtain...
why does heat flows from a high temperature body to a low temperature body?
The above statement can be concluded from applying conservation of momentum to particles of a system containing a high and low temperature bodies.
But in texts, its written that the above statement is a consequence of...
a small object with mass m=10gr is thrown vertically upwards from the surface of Earth with a velocity v=10m/s
i need to find the max height(Hmax) (when v=0) and the time(tmax) when the object reaches the max height by using Newton's second law only.
(ignore the effect of air and air...
Homework Statement
A turntable must spin at 33.3RPM (3.49 rev/s) to play an old fashioned vinyl record. How much torque must the motor deliver if the turntable is to reach its final angular speed in 2 revolutions, starting from rest? The turntable is a uniform disk of diameter .305m and mass...
Homework Statement
Suppose a sphere is rolling on the ground and there is friction. Friction is the only net force acting on it, and by Newton's law, it will accelerate the object in the direction of the force (which is backwards). But the object is actually accelerating forward because...
Newton second law: the net force applied to a body produces a proportional acceleration.
Lets fly a rocket. Rocket has some kind of propulsion system that is producing force, so the rocket should accelerate to the infinity. However when the speed is closing to the speed of light, the...
Homework Statement
a box filled of water is over at the beginning of a incline plane of 30 degree, it has a mass of 1 kg,from the bottom of the plane to the top is 10m, the gallon is pushed with a force of 10N to the top, and the gallon is leaking 0.01kg per second
what is the final velocity...
Hi, I really need some help on these homework problems. Sorry I couldn't paste the pictures in but please help me!
1) When a 58 gram ball is served, it accelerates from rest to a speed of 45 m/s. The impact with the racket gives the ball a constant acceleration over a distance of 44 cm. What...
Homework Statement
A 1300 kg car in neutral at the top of a 17° inclined 10 m long driveway slips its parking brake and rolls downward. At what speed will it hit the garage door at the bottom of the incline? Neglect all retarding forces.
Homework Equations
(sin17)
(cos17)...
Homework Statement
A bullet fired into wet clay will decelerate fairly uniformly. If a 10 g bullet hits a block of clay at 235 m/s and comes to rest in 17 cm, what average force does it exert on the block? [Hint: From the fact that the bullet goes from vi to 0 in a distance s, you can find aav...
I am trying to understand the behavior of blackbodies in interaction with each other.
Conditions as follows.
1) There are two blackbodies, say B_1 and B_2, with corresponding temperature T_1 and T_2.
2) Initially T_1>T_2.
3) B_1 and B_2 have thermal contact only through radiation...
Homework Statement
Find the Net force on the system
see thumbnail for given.
Normal force action on object 1 - 150N
Normal force action on object 2 - 346N
Force of friction action on object #1 - 15N
Force of friction action on object #2 - 34.6N
M1 moves to the left
Homework Equations
F = ma...
Homework Statement
A 90 kg parachutist in free fall has an acceleration of 6.8 m/s^2.
Homework Equations
What is the frictional force provided by air resistance when she is accelerating at this rate?
The Attempt at a Solution
I tried this, assuming down is positive. I used the...
Kepler's law questions
Homework Statement
What effect will the tangential component of force have on the velocity of the planet?
What effect will the normal component of force have on the velocity of the planet?
Homework Equations
The Attempt at a Solution
I think that the...
The person in the drawing is standing on crutches. Assume that the force exerted on each crutch by the ground is directed along the crutch, as the force vectors in the drawing indicate. If the coefficient of static friction between a crutch and the ground is 0.90, determine the largest angle...
Once her chute opens, a sky-diver of mass m is acted upon by a downward force Fg due to gravity, and an upward force Fr due to air resistance. If Fg = mg, where g is gravitational acceleration, and Fr is proportional to velocity v, use Newton’s Second Law of Motion to write acceleration a as a...
Newton's second law and tension!
Homework Statement
A helicopter is lifting two crates simultaneously. One crate with a mass of 139 kg is attached to the helicopter by cable A. The second crate with a mass of 88 kg is hanging below the first crate and attached to the first crate by cable B...
I did a lab earlier this week on Newton's second law with a pulley and carts. M2 was the block that traveled horizontally and M1 was the hanging mass. The mass of the cart that was moving horizontally was constant all experiment with about 0.2 kg. The mass of the hanging gradually increased...
Once her chute opens, a sky-diver of mass m is acted upon by a downward force Fg due to gravity, and an upward force Fr due to air resistance. If Fg = mg, where g is gravitational acceleration, and Fr is proportional to velocity v, use Newton’s Second Law of Motion to write acceleration a as a...
I've heard that the prevailing theory of cosmology before the Big Bang was that the universe is static and eternal. If this is true then how did they reconcile that theory with the second law of thermodynamics?
Thank you...