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What is a newton? (unit)

  1. Oct 22, 2012 #1
    I'm not sure where to put this thread, so I just placed it in here.

    One thing I know is that a newton is the net force required to accelerate an object with a mass of 1kg at a rate of 1m/s2. Now here's one of my questions: if 1N = what I stated earlier, does 2N = the net force required to accelerate an object with a mass of 2kg at a rate of 1m/s2, or, does 2N = the net force required to accelerate an object with a mass of 1kg at a rate of 2m/s2?

    A newton is also a unit of weight for the metric system. Right?

    Can someone please explain to me what a newton is.
     
  2. jcsd
  3. Oct 22, 2012 #2

    davenn

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    your 2 examples are the same

    F = ma = mass x acceleration doesnt matter if its 2kg x 1m/s2 or 1kg x 2m/s2

    F still = 2Newtons


    Dave
     
  4. Oct 22, 2012 #3
    a newton is exactly what you said here: "the net force required to accelerate an object with a mass of 1kg at a rate of 1m/s2"

    as for what 2N is, well it could be either of those things...

    I mean, another way to think of the Newton is that it is the unit of "force". The force acting on something is in the same direction as its acceleration and is equal to the magnitude of its acceleration times the mass of the object.


    "Weight" is what we call "the force due to gravity" in general conversation. So, since weight is a force, that means that it would be described using Newtons.

    But it's not so much that "force" is a "weight" but rather "weight" is a "force".

    Sort of like how not all rectangles are squares but all squares are rectangles.
     
  5. Oct 22, 2012 #4
    So in F = ma, the units are: kg, m/s2, and newtons?

    To clarify what you said, my examples are the same. No difference?
     
  6. Oct 22, 2012 #5

    davenn

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    yes so F (Force in Newtons) = m (mass in kg) x a (acceleration in m/s2)

    so
    m= 1 and a = 2 ... 1 x 2 = 2
    m= 2 and a = 1 ... 2 x 1 = 2

    just be wary of using the term weight instead of mass and underwstand the difference between the two
    understand what SHISHKABOB said in his post :)

    Dave
     
  7. Oct 22, 2012 #6
    There is a difference, in one case you are accelerating a 2kg mass and in the other, you are accelerating a 1kg mass, but they both require 2N. So the acceleration that you see if you apply 2N to an object will depend on the object's mass, but the mass times whatever that acceleration is will be 2N... by definition.
     
  8. Oct 22, 2012 #7
    Hehe, just checking my understanding. Weight is the force due to gravity and mass is the amount of matter in an object? And since weight is the force due to gravity, it is considered a force. And this force is measured in newtons. Am I correct?
     
  9. Oct 22, 2012 #8
    Yes. Weight is the force on an object due to gravity. You can calculate an object's weight by multiplying its mass by the acceleration due to gravity (on our beautiful planet this is 9.8 m/s^2 at sea level)

    That means a 1 kg object weighs 9.8 N. This force is the force exerted on the earth by the object.
     
    Last edited: Oct 22, 2012
  10. Oct 23, 2012 #9
    Don't try to explain any of this to the guys down at the Gym.
    They won't understand and it's guaranteed to get you a 'wedgie'
     
  11. Oct 24, 2012 #10
    Sir Isaac Newton's second law gives the concept of force in the formula: F = ma. This is read as, force equals mass times acceleration.

    In standard international units (SI units) mass is given in kilograms (kg), acceleration is given in meters per second per second (m/s2), and force is given in newtons (N).

    Abbreviated as N, a newton is defined as the force required to accelerate 1 kilogram a meter per second squared; in empty space.

    This concept is expressed in equations of the form, N = kg*m/s2.
    If this were an actual problem, numerical values would precede the associated units. Such as, 8 N = 4kg * 2m/s2.

    A newton is a vector unit that relates both the magnitude and direction in SI. We say the force of gravity is -9.81 m/s2. So the force of 3.6 ounces (~1/9.81 kg) at the Earth's surface is 1N down. We could also say this is -1 N up, they are equivalent.

    Centimeters, grams, and seconds (CGS) were replaced by the SI's use of kilograms, meters, and seconds (KMS). The CGS unit of force is a dyne (dyn); 1 N = 100 000 dyn.
     
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