What is First law: Definition and 229 Discussions

"First Law" is a science fiction short story by American writer Isaac Asimov, first published in the October 1956 issue of Fantastic Universe magazine and later collected in The Rest of the Robots (1964) and The Complete Robot (1982). The title of the story is a reference to the first of the Three Laws of Robotics.

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  1. A

    Chemistry Molecular diffusion question; fick's first law

    Homework Statement Calculate the flux of oxygen across a square centimeter membrane [2\mu, or 2x10 ^{-6}m thick if the concentration on the right hand side of the membrane is 4mL/L and on the left side is 2mL/L. Homework Equations fick's first law of diffusion Flux = dC/dx = D[C2-C1] where...
  2. B

    Newton's First Law straight line speed

    Homework Statement For my A-level homework I have to think whether there are any objects in the universe that move at the same speed in a staight line forever. Homework Equations I am stuck to think of anything - do any exist? The Attempt at a Solution Thanks for the help
  3. U

    Kepler's First Law: Exploring Its Derivation and Problems

    The textbook I'm using states Kepler's first law in the following form: all planets move in elliptical paths with the sun at one of the foci. If I'm understanding this claim correctly, I've got some problems with it.. This conclusion was reached using a potential that depends only on the...
  4. stevebd1

    Dark energy and the first law of thermodynamics

    This has probably been posted elsewhere within the forums but I'm unable to find a thread relating to it. Could some one explain how the existence (and the expected eventual increase) of dark energy doesn't violate the first law of thermodynamics? regards Steve
  5. A

    Newton's 1st Law: Motion & Astronauts

    Newton's first law states that a body in motion tends to stay in motion and that's why when you're driving a car and then suddenly stop you get pushed at the same speed you were traveling. the Earth orbits the sun at 64,000 miles and the Earth's rotation is 1000 miles per a hour. my question...
  6. E

    How Does the First Law of Thermodynamics Apply to Irreversible Gas Expansion?

    Homework Statement A fixed quantity of gas is originally at 20 atmospheres in a volume of 1 litre and a temperature of 300K suddenly expands and comes to equilibrium with a volume of 50 litres and a pressure of 1 atmosphere. If the process is irreversible and involves the transfer of heat...
  7. L

    A traffic accident with Newton's first law

    Homework Statement Consider this situation: A police officer arrives at the scene of an accident and finds a load of straw bales partly on the back of a pickup truck and partly on the hood of a Jaguar sedan. Both vehicles are facing in the same direction. The pickup is in front of the...
  8. R

    Newton's 1st Law: Incl in 2nd Law? Reasons/Ex

    Is included in the second law? Give reasons with examples. :rolleyes:
  9. H

    What is the point of Newton's First Law?

    What is the point of Newton's First Law? The first law says that "The state of motion of an object will not change unless acted upon by an outside force". In layman's terms, this means that the object's velocity won't change unless there is a net force (at least that is how our physics teacher...
  10. ranger

    Question on Newton's first law of motion

    Okay, so its stated that a body in motion stays uniformly in motion unless influenced by an external force. But what happens if that force is internal? For example, a rock moving in space that explodes from the inside. This causes the rock to fragment and move in different directions. This has...
  11. K

    Newtons first law: implications on kinetic energy

    Newton's THIRD law: implications on kinetic energy edit: after thinking about it a little more, I realized something. After having landed, my kinetic energy becomes what it began as (practically zero). nvm then.
  12. E

    Newton's First Law and objects in motion

    Im wondering what situations involving objects in motion , you could take advantage of Newton's first law of motion? I have one situtaion but I am not sure of another one that could be considered taking advantage of Newton's law...
  13. K

    Thermodynamics - First Law (T-fitting)

    Hey guys, I am having a problem trying to figure out what this question is asking for: The air flow in a compressed air line is divided into two equal streams by a T-fitting in the line. The compressed air enters the 2.5cm diameter fitting at 1.6 MPa and 40 deg C with a velocity of 50 m/s...
  14. P

    Explaining Newton's First Law & the Dropped Weight Trolley

    I read the following question in a Yr11 High School Physics Test. A trolley is traveling along at unifrom velocity when a weight is dropped onto it which stays there. The velocity of the trolley will... A) Decrease B) Increase C) Stay the same ? The answer says "decrease"...
  15. R

    Kepler's First Law: Approximation or Exact?

    Hi folks, my problem is the following one: Kepler stated that orbits of planets are elliptic. Everytnig's well since Newton obtained the same results, with his formula for gravity F = G(mM)/r^2 Now, i tried to write the Lagrangian of the system (L = K-U, K is cinetic energy, U is...
  16. C

    Heat and the First Law of Thermodynamics

    Consider Joule's apparatus described in Figure 20.1. Each of the two masses is 1.50 kg, and the tank is filled with 190 g of water. What is the increase in the temperature of the water after the masses fall through a distance of 3.50 m? For this I know that PE=W, and that 2mgh is proportional...
  17. A

    How Does Heat Affect the Expansion of Monatomic Gas in an Insulated Cylinder?

    one mole of monatomic gas (in a perfectly insulated cylinder) has temp = 27 degees c = 300K volume = 0.025m^3 (gas held in frictionless piston) heat suppied causes gas to expand at constant pressure gas expands to volume = 0.06m^3 i) calc final temp.. i used pV/T =pV/T (p cancels...
  18. B

    Solving Newton's First Law: Spider Attached to Two Threads

    Please , Explain me this situation A spider is attached to two threads of equal length that make a 120o angle with each other. The spider is motionless and its mass is m=30mg. What is the tension in each thread? According to the Newton first Law, the sum of the force must be 0...
  19. I

    First Law of Thermodynamics question

    a quantity of gas in a cylinder receives 1600J of heat from a hot plate. At the same time 800J of work are done on the gas by outside forces pressing down on a piston. Calculate the change in thermal energy of the gas Input heat Q = 1600J The amount of work done on the gas is, W = 800J...
  20. G

    What Is Inertia and How Does It Influence Motion?

    :devil: What really is INERTIA? Is it a force.? A vector or a scalar? What can be known only by the defination? Does it really have anything to do with physics?
  21. B

    Need help on difficult Newton's First Law Question

    *Just noticed that I posted in the wrong thread. Sorry about that is there any way I can move it to the right thread?* I have a difficult question and any help would be greatly appreciated. Here it is: To keep Robin from being captured, Batman tosses him out a third storey window, knowing...
  22. S

    Problem dealing with Newtons First Law

    A 75 kg water skier is being pulled by a horizontal force of 620 N and has an acceleration of 2.1 m/s2. Assuming that the total resistive force exerted on the skier by the water and the wind is constant, what force is needed to pull the skier at a constant velocity? ? N
  23. B

    How Does Doubling the Force Affect the Speed of an Arrow?

    I don't understand how to even begin with this problem. Here it is: An arrow, starting from rest, leaves the bow with a speed of 26.0 m/s. If the average force exerted on the arrow by the bow were doubled, all else remaining the same, with what speed would the arrow leave the bow? I do...
  24. M

    Solve 1st Law of Thermo P20.38: Net Work & Energy

    An ideal gas initially at Pi, Vi, and Ti is taken through a cycle as in Figure P20.38 (n = 2.6). Figure P20.38 (see attachment) (a) Find the net work done on the gas per cycle. PiVi (b) What is the net energy added by heat to the system per cycle? PiVi (c) Obtain a numerical value...
  25. G

    First law of thermodynamics and gaining heat

    This is about the system and the surroundings. I am not sure whether the signs are correct: When the system is gaining heat, the sign is positive. When the system is losing heat, the sign is negative. When work is done on the system, the sign is negative. When work is done by the...
  26. W

    Friction make observing Newton's first law of motion difficult?

    Why can friction make observing Newton's first law of motion difficult?
  27. W

    What is Newton's First Law of Motion and how does it explain objects at rest?

    Hey, Could anyone give me good examples of Newton's First Law of Motion? THANKS ALOT, Michael
  28. H

    Newton's First Law of Motion & Skidding on Icy Roads

    I've recently brought a physics book, and in it are some questions, which go throughout different chapters. at the moment i am on Newton's first law of motion. I looked at one of the questions on it and it asks " Explain how a car can skid on a icy road?" I remember reading in the...
  29. P

    About Newts First Law of motion

    About Newts First Law of motion... U kno the first law of motion..."Object has a netforce of zero when its at rest or moving at constant velocity..." I don't get how you could say an object has a total netforce of zero when its moving...If its moving in one direction then isn't a force acting...
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