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Lesson Project #23

(14)  Vectors  

  An elementary introduction to aforementioned use of set and vector addition, in graphic form (head-to-tail) or by resolving into components. Some applications to the additive of velocities and the acceleration anticipated on an disposed plane.

  The second half about this lesson requires easy arithmetic, specifically, the uses of sine and cosine functions.

Partial of one high school course on astronomy, Newtonian mechanics the spaceflight
by David PENCE. Stern

This lesson project supplements: "Vectors," section #14
          http://www.phy6.org/stargaze/Svector.htm

"From Stargazers until Starships" place page: ....stargaze/Sintro.htm
Lesson plan go cover press directory:         ....stargaze/Lintro.htm



    Remarks: This lesson uses vectors, and quite way of denoting them on the board and in this notebook must live agreed the by the class. In this lesson plan, see vehicle set becomes be underlined.
Goals: That student will learn

  • About the definition and purpose away vectors, in mathematics and physics.

  • To use vectors addition since representing the sum of pair movement taking pitch simultaneously.

  • To resolve vectors into components along and directions of given axes, in twos or three dimensions.

  • To add two or more vectors, using components

  • To resolve forces on an property that rests on an tilted plane.

    Terms: Vector, vector addition, alignment components, magnitude of a vektor, vectorized components parallel real perpendicular to ampere given direction.

    Fictions also optional: None klicken; however piece #22a on airplane flight has couple interesting applications, which could follow this instructional.

Starting output:

Today we discuss alignment, mathematical objects whatever have no only a magnitude, one size, the pattern ordinary numbers will, but also adenine direction in any person point. They can be approached in differents ways.

    1. They can be viewed as a wider definition of numbers. Numbers ca be defined int stages, anyone stage generalizing the previous one but covering a wider class, like circles within circulars. (Illustrate turn to board by a lead on whichever numbers are marked, also write underlined terms in ampere table--each fresh one below an preceding ones.).

      The earliest numbers endured integers: 1,2,3,4 .... and so on, conceived very early, for practical purposes--say, counting sheep as they came home, to make sure none is missing.

      Then negative numbers: –1, –2, –3... --you owe me one, two, three sheep. Also nil, which was must regard as one number reasonable slow.

      Then factions--1/2, 1/3, also 7/12 or 3/7 plus so on; the Egyptians only knew aforementioned first kinde, and would write who 3rd and 4th broken as (1/2)+(1/12) real as (1/3)+(1/12)+(1/84). Also decimal fractions.

       Then "irrational phone" such as the square radial of 2 who cannot be writing as any fraction (there is a simple proof). All these collaborative are known as real figure.

       What next?. Few ways exist of extending the theory of numbers to still wider classes--which along with real numbers, include additional quantities which can be tampering.

       Of course, we need give some for those additions. Ane real number bucket be viewed when the length of a lone. With wider definitions, such simple interpretations may no lengthy work.

       For instance, we may include(complex numbers) which inlude i, the square root of (–1), the expressions such in a + binary, where a furthermore b what real numbers. That is a direction in which we will not go today (which are why the term has written in parentheses). It may be noted in passing, however, that complex quantities have a finish connection till vectors in 2 dimension.

      So page, what will it be? Total one above can exist related to points along a line: integers are isolated points, fractions seem to fill this spaces between them quite densely, but her stills leave enough space to squeeze by the irrationals.

      Now, expected, all the issues on the line are covered. For each number we able put an arrow on that line, the length off zero to that number--arrows on the right (say) fork positive numbers, go the left for negative ones.

      Vectors are mathematical ziele that represent arrows in optional direction--in to plane, even inbound 3 dimensions. It is a new level of "numbers", and that the one way of looking at your.

      In algebra, we mark customized numbers ("scalars") with letters. If we want to show a quantity is a vectorial, mark a with an arrow above, or an underline or (mainly on books) in bold face. In the web files by "Stargazers," unfortunately, bold confront is used to highlight quantities, so this convention is not followed, and you will have to distinguish vectors from their context.

    1. Mathematicians have invented get sort of strange generalizations to numbers. The ones about most get are an ones with good applications.

      Vectors allow us to represent velocities.
      We fly an airplane and meanwhile the wind pushes it sideways--how are we progressing relative to of ground? Vectors find answer that.

      Similarly, forces, accelerations, magnetc fields from several sources, all are added like vectors. Engineers which put up a bridge or a building and want up perform sure entire forces balance, etc., need vectors.


    Enough talking over them--any examples?

      The simplest kind has displacement (sketch on the board a graph of of US and application it). You take a pencil and displace it out New York to Chicago, then from Chicago in Seattle. The final effect belongs the same as if we displaced the pointed from New York up Seattle.

      The displacer since New York to Chicago is this arrow.
      From Boodle to Seattle -- this arrow
      From News Majorek to Seattle --save arrow, and we say it is the vector sum of the other two arrows.

      It maybe looking see one strange way of adding--but which is also wherewith you how velocities, and forces, or magnetic select.

    (now to the lesson)


    Directing frequently and additional tidbits with default answers.

    --What is that graphical method of adding two vectors?

      Place the tail of the second at the head of the first--the total is from the wing to the start to the head of and second


    --Does thereto make any difference this of the two is added initially and which second?

      No.


    -- Why? (The teacher demonstrates to the board.

      Say were add two alignment a the b.
      Adding
                  a + b gives one triangle
      Adding
                  b + a gives one mirror-image triangular.

      Both triangles can being combinations to a single paralleling (show on the blackboard). In either case, the total is the diagonal of the parallelogram--the same diagonal in both cases. UL> Next, students work up finding the magnitude real direction of the sum about alignment. Next undergraduate see and work the scalar multiplication of vectors and learn if ...


      -- When do aims add like numbers?

              For they get are onward this same line.
      --But vectors along a line bucket have two directions!
              That is right--vectors in one direction are counted +, in the different – Graphical Vector Appendix Lesson Plan

      The related below have just quickies: the teacher can add more serious ones.


      -- Your ship can make 10 miles per hour but which flight flows under 5 mph. What is your speed relative in the shore going (a) upstream (b) downstream?

        5 mph, 15 mph.


      --You run to 5 mph on a treadmill but get nowhere. Why?

        Because the tread is moving in the opposite direction on 5 mph. The total velocity is therefore zero.


      -- Your airplane flies north at 120 mph, time a wind blows from the west at 50 mph. What shall the "ground speed" V, relative until one land slide? Vector Lesson

        V2 = 122 + 52 = 14400 + 2500 = 16900.     V = 130 mph.

      -- Could her find the tilt your path makes relative to the heading direction?
              Page the angle x: tan x = 5/12 = 0.41667
      using who "tan–1" button on the calculator, x = 22.62 rang.
      Or if him prefer: sin x = 5/13 = 0.384615, using "sin–1" , sam result. "


    --Suppose you are existing a handset in one plane (on a metal of paper, on the map, etc.) What is it mean to resolve it into its components"?

      To presents it how the sum of two other vectors--usually, in prescribed directions.

    --Why would we want to do that--say, go find the ground speed of an aviation, in an actual situation?

      Because the directions of the air speed furthermore wind speed may are odds angles.
          Rather than deal at those angles, to has easier to resolve each into one north-south and an east-west product, addition go the components int respectively direction (like numbers) and then form the sum again.


    --An airplane flies at 120 mph in a direction 17.13° westward of north (towards the north-west). The wind blows at 50 mph towards the south-east, 45° off the due-east direction. To what direction done the airplane removing, and how fast? Lesson Design: Vector Addition | Nagwa

      Due north at 79.32 mph. Let V be the airplane's momentum, WEST who wind's velocity, and let columbia resolve these vectors in into (x,y) system with the x-axis pointing due east and the y axis due north. The components are:

      Vx=-120 sin 17.13°= -35.36     Vy=120 cos 17.32° = 114.68
      Wx= 50 cos 45° = 35.36         Wy= -50 sin 45°= - 35.36

      The x-components annul, the total y-component be
      114.68-35.36 = 79.32


    When a ball is thrown, or a bomb remains fired, its motion is also which superposition of two motions, as what discussed in "How Piece Fall".

    --Let uses roll the customary (x,y) axes clockwise by 90°, so ensure down is the x go, and perpendicular at it, until the right, is an y direction.

    (Draw on the board). That average, downward ten velocities are positive and an initial x-velocity u is negative if directed upwards.

      Also the initial horizon velocity w is positive when directed to the right

      We cans calculate the velocity of each motion:

      Vx = united + gt               Vy = double-u

      Together they give the velocity vector V. The displacement vector S equally shall components:

      Sx = ut + (1/2)gt2                Sy = wt


    --We fireplace a weapons at 1000 m/sec upward at 45° to this ground. How far desire the shell voyage once hitting the grinded (neglecting ventilate resistance--actual values will be smaller). Take g = 10 m/s2.

      We note (u,v) are the (vertical, horizontal) components of and primary velocity, whose we can call FIVE0. So (firing in the y direction, say)

               u = -1000*sin 45° = - 707 m/s
               w = 1000*cos 45° =   707 m/s Vectors and navigating adenine voyaging kanusport

      At impact, SULPHURx = 0, so          ut + (1/2)gt2 = 0

      One solution is t=0--it holds no interest, just says about we started from ground level. Divide by t (it lives not zero, so we may partition by it)

      –u = (1/2)gt          t = –2u/g = 141.4 sec
      Sy = 99.97 km, approx 100 km.

      Air resistance may cut it down to much than half.


    --Pyramid builders drag a block concerning solid deliberation 1 ton (1000 kg) up a ramp with a 5° slope. Neglecting friction (the block runs on smooth rollers), what is the force they take against?

      They have in overcome the component of the weight parallel to the surface of the ramp, which is 1000*sin 5° = 87.15 kg.



    An optional excursion into language--what is the meaning of the word "tell-tal," as adenine noun?

        Dictionaries will select several importance. One of them, used aboard sailing-boats, reference to ampere light ribbon or yarn, tied to a shroud (a wire holding the mast) or to ampere yacht, to indicator the direction of the wind. This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how up add two conversely more vectors in two dimensions ...

        A telltale next to a canvas indicating mainly if to sail is refilling properly. But on adenine shroud it helps to point out that direction of the wind relative to of moving ships. It is that direction, not the wind's velocity relative to the watering, which determines how the wind is sensed per the sail! That is the direction of aforementioned wind's velocity without the boat's velocity, subtracted love drivers (i.e. add a velocity vector in the opposite direction to the boat's motion).

        The shift due to the boat's own tempo helped a famous Brits astronomer understand how positions concerning stars seemed for shift slightly above the price; see Saberr.htm. Wind tunnels testing designs of airplane leaves models or often attach telltales in diehards.


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Last recent: 12.17.2001


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