Laws Definition and 1000 Threads

Homework Statement A glass tube filled with air at room temperature is 1.54m long. The tube is closed on one end, and open on the other. When submerging the open end in water, the water in the tube rises by 0.14m. How much of the tube is above the water's surface? The correct answer is 0.40m...

Homework Statement http://[url=http://postimg.org/image/f7e6kp0xv/][PLAIN]http://s21.postimg.org/f7e6kp0xv/image.jpg Homework Equations Kepler's laws The Attempt at a Solution I thought the answer will be C : I and II But the solution written (it was my friends book) is B, which is correct?

Are their specific laws or rules in emergence? For example, temperature is emergence from the underlying particles. Superconductivity is emergence from the cooper pairs. It seems you can turn off emergence by say increasing the temperature to disable the cooper pairs. In temperature, how do you...

Homework Statement If number of molecules in a closed container increases and it is kept at a constant tempurature, what happens to the pressure? I was confused because I thought if you add molecules the temputature would go up so keeping temputature a constant would have no affect on the...

In my textbook, it makes the leap from $2(2^{n + 1}) = 2^{n + 2}$ citing the laws of exponents. I'm not sure which law of exponents it is referring to. Thanks

The laws of thermodynamics deal with the irreversible flow of energy. Conservation of energy is the first law and increasing entropy (disorder) in an energy flow is the second. The conservation of mass is the equivalent first law for matter. It is commonly recognized. But what about the...

At 265 SM, and age 1.7 Million years, at 163,000 Light Years Away in the R136 cluster, is R136a. But, it shouldn't be alive now. It should have exploded given the model of Solar Mass Evolution at 200,000-375,000 Years old of age. It's in it's Wolf-Rayet phrase, but it still shouldn't be alive...

Homework Statement A book of mass m is sitting on a table of mass M. Which of the following statements regarding Newton's Laws of motion is true? (a) Newton's Third Law says that the magnitude of the normal force from the table on the book is equal to mg. (b) Newton's Second Law says that the...

Homework Statement what is the value of F needed so that block begins to move upward on frictionles incline plane . Homework EquationsThe Attempt at a Solution i made an attemp and got the answer - Mgtan(thetta) but the real answer is - mgtan(thetta/2)

1. Which will have the greater force during impact; a bumble bee being hit by a train or a train being hit by a bumble bee? (Hint: Newton’s Three Laws of Motion) 1. What is the centripetal force that holds the Earth in orbit around the sun? 1. How much does a 76.0 kg person weigh on Earth in...

Homework Statement [/B]A 10g bullet accelerates from rest to 500m/s in a gun barrel of length 10cm. Find the accelerating force (assuming it is constant).Homework Equations F=ma, v^2=vo^2+2a(x-xo)? The Attempt at a Solution I tried using F=ma, but it does not equal the answer in the back of...

What role do theories, models, and laws play in the scientific process? Is there a clear dividing line between a theory and a law? Are models used in both theories and laws? All theories and laws? Do our best current models perfectly represent reality to the best of our knowledge, or are they a...

Hi, In general relativity we have no general conservation of energy and momentum. But if there exists a Killing-field we can show that this leads to a symmetry in spacetime and so to a conserved quantity. Thats what the mathematic tells us. But I don't understand what's the meaning of an...

Considering the multiple universe view, if a measurement (or something else) makes visible which universe we are in, is it then also possible we find ourselves in one with (slightly) different laws of nature?

Homework Statement [/B] In the circuit shown below if Vs = 5V, use Kirchhoff’s Laws to determine the currents i1, i2, i3 and the source current is. Calculate the power dissipated by the resistors in this circuit. Confirm that the power dissipated by the resistors is the same as the power...

I have been preparing for a 9 Th grade talent exam and i can get my head around this problem I keep getting the same answer 5, i used fbd The answer is 7 ; help me out where am i wrong

Hello, this isn't really a physics question but I'm getting pretty desperate and you guys have always been able to help me out before :) 1. Homework Statement http://imgur.com/mYtJDLI Homework Equations I believe I'm suppose to use the Laws of Exponents. For the first set possibly but not...

So, we're learning about forces and Newton's laws in class, and my professor zips through the material without really explaining anything. I'm having the most trouble understanding f_net=ma (specifically, how that can be used in a free body diagram) and how third-law pairs fit into a free body...

I am a first year student and i am required to build one thing based on one physics law . if i build a rubber band powered airplane , what laws should i say it applies? and what about rubber band powered car??

Hey, Anyone know any good workshetts, pdf wise or a document with good questions about Newtons laws. What i mostly look for is, Incline plane questions, atwood machine questions with pulleys in different ways, half atwood machine questions. Etc. Very classical problems. Glad if U could help...

In a previous thread, the OP asked for answers at the "I" (i.e., undergraduate) level to the following question: S/he received a variety of contradictory answers, and the discussion may have been hindered by attempts to present more sophisticated mathematical ideas as the appropriate level...

If anyone could tell me how to answer these questions that would be fantastic. Thank you so much! 1. A box that weighs 66.2 N on Jupiter is taken to Pluto. The weight of the box on Pluto will be ____. (acceleration on pluto is 0.42) Would you find the mass first? 2. The hand in the image...

Homework Statement Prove ##A\setminus(B\cap C)=(A\setminus B)\cup(A\setminus C)## Homework Equations 3. The Attempt at a Solution [/B] We will show that every element in ##A\setminus(B\cap C)## is contained in ##(A\setminus B)## or ##(A\setminus C)##. If ##x\in A\setminus (B\cup C)## then...

Is there an equation which combines Newton's equation of calculating the gravitational force between two masses with that of Coulomb's equation of describing the electromagnetic force between two particles? In other words, does an equation exist which describes the relationship between mass and...

My Physics Professor from my Physics 1 class says Newtons laws are wrong? Don't get me wrong, but he is a amazing physics professor! One that does not talk to you as if you are dumb or as if he is better than anyone! I love physics and I'm hoping to go into physics engineering, but that's not...

Homework Statement A 1900 kg car moves along a horizontal road at speed v0 = 23.6 m/s. The road is wet, so the static friction coefficient between the tires and the road is only μs = 0.218 and the kinetic friction coefficient is even lower, μk = 0.1526. The acceleration of gravity is 9.8 m/s2...

Does the relativity of simultaneity imply the impossibility of non local conservation laws?

Homework Statement For which non-zero value of x is the equation -x^ -4 = (-x)^ -4 true? Explain. Homework Equations None. Other than applicable exponent laws. The Attempt at a Solution I know how to use the guess and check method. But I was wondering how to reach the answer faster and how...

An open knife edge of mass 200 g is dropped from height 5 m on a cardboard. If the knife edge penetrates distance 2 m into the cardboard, the average resistance offered by the cardboard to the knife edge is:

klotza submitted a new PF Insights post Scaling Laws and the Speed of Animals Continue reading the Original PF Insights Post.

Hi, My instructor gave us a challenge problem to solve in limits: ##\lim _{ x\rightarrow \infty }{ \left[ { x }^{ 2 }\left( 1-\cos { \frac { 5.1 }{ x } } \right) \right] } ## Note that we did not take Hospital's rule yet so we couldn't have used it. Now my first thought was to use the...

Homework Statement Two glass vessels M and N are connected by a closed valve. M contains helium at 20 °C at a pressure of 1 × 10^5 Pa. N has been evacuated, and has three times the volume of M. In an experiment, the valve is opened and the temperature of the whole apparatus is raised to 100...

I've searched a little bit and found that I can derive kepler's third law from Newton's law of gravitation. That's okay. But I want to deduce kepler's second law too: "An imaginary line joining a planet and the sun sweeps out an equal area of space in equal amounts of time". I know it's possible...

Homework Statement two particles of 2 kg and 3 kg are at rest . a 6 N force is exerted on the 3 kg particle at t=0. what is the speed of the center of mass at t=5s? Homework Equations F=ma v=u+atThe Attempt at a Solution first i applied f=ma to the 3 kg object and got 2 as the accn. And...

In the arrangement shown in the figure, find the acceleration of M in upward direction. The pulleys are light. The strings are mass less and friction between the string and the pulleys is negligible. The options are given. The final answer is (B) and this was the solution: I don't...

What is the best way to make a 9th grader understand the concept of force and laws of motion. Also please refer a book where he can get a good practice to solve force numericals. Please mention the ISBN code of the book also. Thanks a lot

hello I've just started learning physics my question is why do force increase while falling and stay constant while on the ground.i know force is increasing because in free fall things accelerate which according to Newton first law force must also go up. the force of gravity of Earth is 9.8N...

If G is a finite set closed under an associative operation such that ax = ay forces x = y and ua = wa forces u = w, for every a, x, y, u, w ##\in## G, prove that G is a group. What I attempted: If we can prove that for every x ##\in## G, x##^{-1}## is also ##\in## G, then by the closure of the...

I have always thought that all of "Classical Mechanics" can be explained with Newton's Laws and a few force equations (e.g., gravitational and Coulomb). In particular, the concepts of energy and torque are convenient but not necessary. If this is true, then can you explain with Newton's Laws -...

Homework Statement Three boxes are in contact with each other on a frictionless horizontal surface as shown. The masses of the boxes are m1 = 10 kg, m2 = 20 kg, and m3 = 30 kg. A horizontal force F = 90 N is applied to m1. Calculate: a. the acceleration of the three boxes. b. the net force on...

Hi there, Now this goes against everything I know as a physicist, but I can't get my head around how thermionics behave when you have an emitter at slightly lower temperature but much lower work function, and a collector at higher temperature and higher work function, so that thermionic current...

Dear PF Forum, Before I go further, I'm stuck and need clarification. Two postulates of SR 2. the velocity of light is the same for all inertial observers. Okay..., this one I can understand, at least can grasp. 1. the laws of physics are the same in all inertial frames of reference; What laws...

I am confused about the current physics regarding neutrinos and implications about the conservation laws of mass-energy and linear momentum. I have read the threads listed for similar discussions, including, "How does conservation of energy/mass apply to neutrinos?", and none of them seem to...

Do we understand how the physical laws of the universe created biology? How can we explain cell division, consciousness, evolution, as a product of matter operating in a universe governed by laws?

Hi, I'm trying this summer to finish my mathematical methods book. I'm investigating right now the chapter of complex numbers, the end of the chapter has some applications in electricity and how can complex numbers make the work easier. The problem is that I didn't found it easier nor...

How did Kepler derive his laws of Planetary Motion without knowing about Newton's law of gravitation? Specifically, the first law of planetary motion which says that planets follow elliptical paths - how did he figure that out without the knowledge of the gravitational pull of the sun? Was it...

What ensures conservation of energy and conservation of momentum in Electron-Positron annihilation? If e=mc2 and momentum = mass*velocity, couldn't the energy equivalence of the electron and the positron be converted to make one photon, or more that 2 photons? I've read that two photons are...

In QM there is no cloning theorem that says "we can't clone or erase quantum state". But in classical macro world we can copy information and erase it. If we should describe classical information as a very complex quantum state then we shouldn't be able to copy or erase it, right? And obviously...

Homework Statement A monkey which has a mass of ##m## is hanging on a rope as the picture shows. Then the monkey starts to move upwards with speed ##u##. Find how the box which has a mass of ##2m## will move. Neglect friction between the rope and pulleys. Assume that pulleys are massless...

Homework Statement Question: Figure 1: QUESTION ABOVE. Homework Equations The Attempt at a Solution :[/B] P + P → K+ + K- + P + P Firstly, I just wanted to check that this is correct. I found the answer pretty quickly by googling it but have since spent a long while trying to understand...