Recent content by late347

  1. L

    Basic probability, conditional probability

    Is the intersection probability such as P(E ∩A) correctly calculated? I was googling about that thing and I just became more confused by the fomrula I found. Something like "the general multiplication rule of probability" The examples that we had in class were mostly about simple things like...
  2. L

    Basic probability, conditional probability

    Homework Statement what is the probability that a component which is still working after 800 hrs, will last for at least 900hrs Homework Equations conditional probability P(E|A) = ( P( E ∩ A) ) / ( P(A) ) The Attempt at a Solution Im just checking my own understanding if this problem...
  3. L

    Confused about integrating acceleration to get velocity

    So, when you have the so-called dummy variable... I don't get it why it is called dummy variable? I thought that the variable matters because the definite integral should be like, essentially... the limit of the Riemann sum. So.. I suppose if we don't do the actual limit, but just think about...
  4. L

    Confused about integrating acceleration to get velocity

    ok, but mathematically speaking the integral function ##v(t)= t^2+t##is defined in the real numbers, I suppose it makes more sense to think about the thing from the physics point of view though, like you suggested the function itself does go under the t-axis such as v(-0.5)=-0.25
  5. L

    Confused about integrating acceleration to get velocity

    Homework Statement acceleratin as function of time ##a(t)= 2t+1## we know that v(0)=0 and s(0)=0 find v(t) find v(5) find s(t) find s(3) and I was thinking about also what happens when t is negative number, is it possible to find also v(-2)? what about s(-3)? Homework Equations integration...
  6. L

    Vector dot product and parallel vectors

    I see, thanks for your input though. Studyin math always seems to bring out new tidbits like this. Especially studying math in English (not my native language):smile:
  7. L

    Vector dot product and parallel vectors

    not really. I was taught about this dot product thing on Wednesday. I was just a little bit confused by the quote in the textbook which discussed a general casse of vectors a and b. There was the statement that if a and b are parallel, then it follows that the angle is zero... But that...
  8. L

    Vector dot product and parallel vectors

    Homework Statement show that points P, Q and R are in a straight line P (1, -3, 4) Q ( 2, 2, 1) R (3, 7, -2) and find the vectors ## \vec{PQ} ## and ## \vec{QR} ## Homework Equations The Attempt at a Solution In proving that the points are in a straight line, we might be able to use dot...
  9. L

    News Studying completely on tablets and devices...

    I really liked taking pictures of the teacher's scribblings on the blackboard during physics classes. It's not quite the same as doing all thw studying on electronic devices but taking snapshots witj smartphone during class does free up some effort on your part to better focus on the lecture I...
  10. L

    3-D vectors forces exerted upon a mast

    please elaborate if you have the time my brain is about to freeze at this point with this exercise. I suppose with some more effort I could solve the system of Equations manually, but... I think even my textbook used an equations solver in some of the worked examples. I was reading my...
  11. L

    3-D vectors forces exerted upon a mast

    A simpler solution would be welcome if anybody has got this figured ouit... I can ask the teacher in a couple of days if this was incorrect or correct...
  12. L

    3-D vectors forces exerted upon a mast

    part C give the form of the force vector ## \vec{r_3} ## when its magnitude is 800 N the cable R_3 is parallel to the force vector r_3 cable R_3 is of the following form ## R_3 = x*\hat{i} + y* \hat{j} - 30\hat{k} ## length of the cable is unknown and was not part of any information that...
  13. L

    3-D vectors forces exerted upon a mast

    small r vectors are force vectors, where as capital R vectors are really just the lengths of the cable which goes from the top of the mast to the ground.(i.e. xy plane) My interpretation was that the arrows are the force vectors because they are "floating around" with no endpoint. Where as the...
  14. L

    3-D vectors forces exerted upon a mast

    Homework Statement The thick arrows represent forces exerrted upon the mast Let ## \vec{r_2} = ~~the~~ longer~force~ vector~~## ## \vec{r_1} = ~the ~shorter ~force ~ vector## correspondinly ## \vec{R_2} = cable ~~2## ## \vec{R_1} = cable~~1 ## r_1 is in the same direction as R_1 r_2 is in...
  15. L

    Constructive interference with sound -- word problem

    After some tabulating of values and some wolfram alpha calculations I used my formula ## \Delta X = n * \frac{\lambda}{2} ## where ## n = [2, 4, 6, 8 ...] ## ## \sqrt{a^2+11.56} -a = n * \lambda / 2 ## ##choose~~ n = 2 ; a = 5m ## first maximum ##choose~~ n= 4 ; a \approx 1.7151m ## second...
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