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Julie

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Questions17
  • Why is my youtube video quality so bad?

    I uploaded this film in high definition. But for some reason it looks dreadful.

    https://www.youtube.com/watch?v=FmjKNeXkW9E

    Youtube thumbnail

    &feature=youtu.beAny ideas? It has some copyright claims currently under review, but I'm not sure if that would effect the processing. Thanks.

    1 AnswerYouTube3 weeks ago
  • Please translate this French into English?

    There is a small part of this Jean Cocteau film on youtube I need to understand in English, but as usual the subtitles are far from clear.

    https://www.youtube.com/watch?v=9vo9GmMsriQ

    Youtube thumbnail

    It's at the part between 1:25:36 and 1:26:00, particularly the narrated sentence when the two characters are scaling the wall, ending "....inexplicable breath".

    Thanks.

    4 AnswersLanguages1 month ago
  • Calculus questions distance?

    I need help working these out...

    1) A particle is moving along a straight line through point O. It's position s cm from O after t seconds is given by

    s = 4t³ - 12t²  + 9t

    Find the distance traveled during the second second after passing O

    I'm taking it that the initial position O is (0, 0), and thus it wants the interval between t = 1 and t = 1.5 (since the it returns to the initial position at 1.5 seconds)

    But if I use f(1.5) - f(1) it doesn't give me the given answer of 3 cm, so please tell me what I am doing wrong here.

    2) O and P are points on a  line. A particle moves along a line in such a way that, t second after it is at O, its velocity is 6t - t². At the time when t = 6, the particle is momentarily at rest at P.

    Find the average speed of the particle between O and P.

    Thanks

    1 AnswerMathematics2 months ago
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    Trigonometry: plane, wind speed and wind direction?

    I'm not understanding this question too well and have drawn it below as I've visualized it (not drawn to scale).

    If a plane is travelling due north 320 degrees with an air speed of 300 km/h, and has a track (drift?) of 325 degrees and ground speed 280 km/h, work out the speed of the wind and its direction.

    I have the speed at 35 km/h, and the direction is 271 degrees due north, whereas the answer is 89 degrees. I can see that this is the part of the upper circle that's missing, but I can't understand why its 89 rather than 271. 

    Thanks.

    1 AnswerPhysics2 months ago
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    Trigonometry: planes, ground speed and drift?

    I'm having difficulty with working out the ground speed and track with the triangle of velocities.

    It seems quite simple but the rules I'm applying don't seem to give the right answers to the questions, so I must be visualizing the problems wrong. I've drawn how I've interpreted one of them below.

    Question: find the track and ground speed when

    Plane travelling at 425 km/h at course 120 deg 

    Wind speed 75 km/h from 270 deg

    (I'm taking it for granted that track is the same as drift, and that the wind is blowing *from* the direction given, though I've tried it both ways and still got the wrong answers).

    My answers for the ground speed are 467 km/h, but real answer is 491 km/h

    Thanks.

    2 AnswersPhysics2 months ago
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    Where has my sine rule gone wrong?

    In triangle ABC, AC = 2.59 cm, BC = 9 cm, and <C = 75 deg

    I'm trying to find the length of AB using the sine rule but somehow I'm doing something wrong....

    9/sin A = 2.59/sin B = AB/sin 75

    9/sin A = 2.59 x sin 75 = AB x sin B

    9/sin A = 2.59 x 0.96593 = AB x sin B

    9/sin A = 2.5017 = AB x sin B

    9/2.5017 = sin A = AB x sin B

    But here I get stuck because 9/2.5017 = 3.597, but there is no arcsin for 3.597...

    Where did I go wrong? Thanks

    4 AnswersMathematics2 months ago
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    Find the length in this sphere?

    A sphere whose centre is O and whose radius is 10 cm floats in water. The water-surface meets the sphere in a circle of radius of 6 cm, and two points A and B are somewhere on this circle.

    Calculate 

    (i) The height (h) from the centre of the circle to O

    (ii) The largest possible value of x (= AOB)

    The second question would be easy if I could workout the first, but I'm not sure how to do this...

    Thanks.

    2 AnswersMathematics2 months ago
  • Algebraic triangle question?

    1) A right-angled triangle has an hypotenuse of length (x + h), and the other two sides are of lengths x and 2h.

    If A is the set of all such triangles with x and h integers, and 1 ⩽ x ⩽ 20, find n(A).

    I'm not sure what this means and need help understanding it, for one, wouldn't Pythagoras' theorem make the triangle x² + 4h² = x² + 2xh + h²......which is impossible....

    Thanks

    1 AnswerMathematics3 months ago
  • Simple volume questions?

    1) A copper wire is 200 metres long and has a  cross section 1.4 mm.

    Calculate the volume, and also the weight when it is rolled up , at 8.8 g per cm³ 

    My answer is 271.04 kg, but actual answer is 2.71 kg, so I am not seeing where I have to divide by 100.

    i. e. 200,000 x 3.1416 x 0.7² = 308 m³

    308 m³ = 30,800 cm³

    30,800 x 8.8g = 271,040 g = 271.04 kg

    2) In this question it looks like the answer in my textbook is wrong.

    Two cylindrical saucepans have the same height, but the smaller pan has diameter of 15 cm and holds 1 litre of water. Calculate the diameter of the larger saucepan if it holds 2 litres.

    Smaller: h x  π x 7.5² = 1,000 cm³ 

    h x π =1000/56.25 =17.7777

    h = 17.7777/π = 5.659 cm

    Larger: 5.659 x π x r² = 2,000 cm³ 

    π x r² = 2,000/5.659 = 353.419

    r² = 353.419/π

    r =  √ 112.497 = 10.6065

    diameter of larger pan = 10.6065 x 2 = 21.21 cm

    But my textbook gives an answers of 15/√2 (= 10.61). This seems a mistake in that it has given me the radius rather than the diameter, which it asked for. Or have I not seen something? Thanks.

    3 AnswersMathematics3 months ago
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    Simple area/volume questions?

    I got these two simple questions wrong and can't see why...

    (i) The area of the image below (6 x 6) - (1 x 4 x 0.5) = 36 - 2 = 34 cm²

    Actual answer: 42 cm²

    (ii) A tetrahedron has a base with sides 3cm, 3cm and 4cm and a height of 4 cm. Calculate its volume.

    Base area = (3 + 3 + 4)/2 = 5

    √5(5 - 4)(5 - 3)(5 - 3) = √20 = 4.472 cm² 

    (4.472 x 4)/3 = 5.963 cm³

    Actual answer: 17.89 cm³

    Could these be misprints in my textbook? Thanks.

    2 AnswersMathematics3 months ago
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    Question on loci and sets?

    The three functions below represent three loci of the variable points P1,. P2 and P3

    P1 a circle about (0, 0) , P2 a circle about (2, 0), P3 a straight line x = 1 (...a perpendicular bisector between 0 and 2) 

    I'm asked to sketch these on a coordinate plane and show a set that qualifies

    P1 ∩ P2 ⊆ P3       ......and find the elements/coordinates of that set, which are {1, +/-√3} 

    But my simple question is this: Can this set also be represented as P1 ∩ P2 ∩ P3? 

    And what is the difference either way? Can't I just also state it as  P3 ∩ P1 ⊆ P2 And does it matter? All three are equally intersecting, so what warrants one or the other being a subset rather than a intersection? (maybe it has something to do with the infinite set of P3...?) Thanks.

    1 AnswerMathematics3 months ago
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    Question on loci and sets?

    The three functions below represent three loci of the variable point P

    P1 a circle about (0, 0)

    P2 a circle about (2, 0)

    P3 a straight line x = 1 (...a perpendicular bisector between 0 and 2)

    I'm asked to sketch these on a coordinate plane and show a set that qualifies

    P1 ∩ P2 ⊆ P3

    .......and find the elements/coordinates of that set, which are {1, +/-√3}

    But my simple question is this:

    Can this set also be represented as P1 ∩ P2 ∩ P3   ...?

    And what is the difference either way?

    Can't I just also state it as 

    P3  ∩ P1 ⊆ P2

    And does it matter? All three are equally intersecting, so what warrants one or the other being a subset rather than a intersection?

    Thanks

     

    Mathematics3 months ago
  • What is the loci of P?

    I'm having trouble with this question because it gives no illustrations, and the answer is simply "half plane, half space". 

    I'd be grateful if someone could illustrate the answer or direct me to the right tutorial that might help me.

    P is a variable point and all other points A and B are fixed. Find the locus of P if

    <PAB is equal or less than 90deg

    Thanks.

    2 AnswersMathematics3 months ago
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    Circle Theorum: what are the angles?

    Both images are not drawn to scale...

    The first one should be easy and I'm sure its 110, but my textbook gives 70.

    But isn't angle x the same as the angle opposite 110?

    In the second I can't quite work out how z is 150.

    Thanks.

    1 AnswerMathematics3 months ago
  • How to format page settings in Apache Open Office 4?

    I want to set the page formatting to columns after a certain page number, but all I can seem to do is set the whole document to columnar form.

    Is it possible to set the page number and have only pages below this number in columns? Thanks.

    Software3 months ago
  • Variation and proportion question?

    How can I understand this question more clearly?

    H consists of a sum of two quantities, one of which varies as the square of r, the other is inversely proportional to r. If

    H = 1 when r = 3

    H = 2 when r = 4

    find H when r = 5.

    I have read this as H = (kr^2)/x

    then x = 9k, k = 3.555......but I'm guessing I'm going in the wrong direction.

    Please help.

    Thanks.

    1 AnswerMathematics3 months ago
  • Simple question on sets?

    Why does 1/x > 2 become {0 < x < 1/2}

    and not simply {x < 1/2}? 

    Where does the 0 come from if no other limits are given?

    Thanks

    2 AnswersMathematics3 months ago
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    What is the ratio of the areas of triangle to trapezium?

    On the triangle ABC X is the midpoint of AB, and Y is the midpoint of AC

    2XZ = ZY

    Find the ratio of the area of the triangle AXZ to that of the trapezium BXYC

    The question doesn't state whether the triangle is an equilateral, and I gather that AXZ:AZY is 1:3.

    2 AnswersMathematics3 months ago
  • What is the surface area of this cylinder?

    Two similar cylinders have volumes in the ratio a³:b³. 

    The total surface area of the smaller cylinder is 20 cm²

    What is the total surface area of the larger?

    The way I am going about this is..

    Length scale factor = x = x¹

    Area scale factor = ? / 20 = x²

    Volume scale factor = √(b/a) = x³

    But I can't get the unknown quantities.

    The answer is (20b²)/a², so I can see that I'm meant to get to 20 x b²/a².

    Please fill me in. Thanks.

    2 AnswersMathematics3 months ago
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    What is the ratio of the areas of triangle to trapezium?

    On the triangle ABC X is the midpoint of AB, and Y is the midpoint of AC

    2XZ = ZY

    Find the ratio of the area of the triangle AXZ to that of the trapezium BXYC

    The question doesn't state whether the triangle is an equilateral, and I gather that AXZ:AZY is 1:3.

    But am I right in assuming that the ratio of the triangle AXY:BXYC is 16:33, and that this holds for all triangles, as long as X and Y are midpoints? This might be where I'm going wrong...

    Mathematics3 months ago