Recent content by albert1993

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    If f is continuous on [a, b], then f is bounded on [a,b].

    Hmm I don't think that's a typo. Isn't he saying that [a,x] is bounded, [x,y] is bounded, and therefore [a,y] is bounded? Oops that was a very poorly worded question as well on my part... I meant: So we have [a,x] is bounded above from the first part("we note there exists x∈S such that...
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    If f is continuous on [a, b], then f is bounded on [a,b].

    I don't see why we just don't get f is bounded on [a,y] right away from the second part. Why does it only prove that it's bounded on [x,y]? See below for revised question I don't see how what logic this is supposed to be... Can anyone elaborate?
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    Motive behind the proof in f(x+y)=f(x)+f(y) is continuous

    Homework Statement The problem is: Suppose f is a function with the property f(x+y)=f(x)+f(y) for x,y in the reals. suppose f is continuous at 0. show f is continuous everywhere. I saw this post as an alternative solution that doesn't use epsilon-delta...
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    Bending Wires and Magnetic Fields?

    Thank you!
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    Bulbs connected in series power consumed

    Draw the figure described. Assume the current flowing is A and the total voltage is V. Now the voltages in each bulb should be P1/A and P2/A. If we add we should get (P1+P2)/A = V. We are looking for Ptotal here which is VA. Thus P total = VA = P1 + P2
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    Bending Wires and Magnetic Fields?

    Homework Statement see attached. this question is from a test that doesn't allow any calculators and usually makes students solve the problem in 1 minute max. Homework Equations perhaps biot savart is to be used? but I doubt that can be done in the time limit... The Attempt at a...
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    What is the Direction of Orbiting Planets around the Sun?

    Happy New Year Everyone! Anyways, I have an interesting question. I have no background on astronomy, but came across some of it while studying for AP Physic C - Mechanics, where it covers Kepler's law and such. Although this was random, I wondered about this: If there are a lot of planets...
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    Normal Force Explained: What It Is & Why It Exists

    So I was wondering what normal force exactly is and why or how it exists. Can someone help me understand it? A link to some page describing it would be great too. Thanks.:)
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    Resistance of a Spherical Wire

    So I am doing elementary physics, as in high school elementary, and learned that the equation for the resistance of a wire can be put in the form: \rho\frac{\ell}{S} so what about a wire that is in the form of a sphere? (let's say something like that can exist :), or you can prove to me that it...
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    Is a*b equal to LCM(a,b)*HCF(a,b)? Help me understand the proof.

    hcf(a,b) is going to be all the common factors of a and b right? so if we make a and b in the form that in3 made, we find that they share some p_n's, right? so whatever is smaller, thus min (e_n, f_n), will become a common factor of a and b. if we multiply all of these we get hcf (a,b) and...
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    Direction of an object when the net force is 0

    ok, thank you :biggrin:
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    Direction of an object when the net force is 0

    kk, so is it impossible to determine the direction of an object when the net force is 0, unless we know what its original direction was (that is if it was moving in the first place), right?
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    Direction of an object when the net force is 0

    ahh so you're saying that there is no direction of an object when the net force is 0?
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    Direction of an object when the net force is 0

    i meant time as, that there was a moment of time that the the net force was not 0 before they all became equal
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    Direction of an object when the net force is 0

    i'm sorry.. i don't understand what you mean... but i think i got my question answered..
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