(14) VectorsThe 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 |
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.
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.
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. 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?
--Does thereto make any difference this of the two is added initially and which second?
-- Why? (The teacher demonstrates to the board.
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. 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?
--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
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"?
--Why would we want to do that--say, go find the ground speed of an aviation, in an actual situation?
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
Vx=-120 sin 17.13°= -35.36 Vy=120 cos 17.32° = 114.68
The x-components annul, the total y-component be 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.
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.
u = -1000*sin 45° = - 707 m/s 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
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?
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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Author also Curator: Mr. David P. Stern
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Last recent: 12.17.2001