Presentation on theme: "An Introduction with Components September 19, 2013"— Presentation transcript:
1An Introduction with Components September 19, 2013 VectorsAn Introduction with ComponentsSeptember 19, 2013
2There are two kinds of quantities… SCALARS are quantities that have magnitude only, such aspositionspeedtimemassVECTORS are quantities that have both magnitude and direction, such asdisplacementvelocityacceleration
3R R R Notating vectors head tail This is how you notate a vector… Books usually write vector names in bold.RYou would write the vector name with an arrow on top.This is how you draw a vector…Rheadtail
4A Direction of Vectors x Vector direction is the direction of the arrow, given by an angle.Draw a vector that has an angle that is between 0o and 90o.Ax
5 Vector angle ranges x y Quadrant II 90o < < 180o Quadrant III180o < < 270oQuadrant IV270o < < 360o
6B Direction of Vectors x What angle range would this vector have? What would be the exact angle, and how would you determine it?Between 180° and 270°xor between-270° and -180°B
7Magnitude of VectorsThe best way to determine the magnitude of a vector is to measure its length.The length of the vector is proportional to the magnitude (or size) of the quantity it represents.
8Sample ProblemIf vector A represents a displacement of three miles to the north, then what does vector B represent? Vector C?BAC
9Sample ProblemIf vector A represents a displacement of three miles to the north, then what does vector B represent? Vector C?BAC
10Equal VectorsEqual vectors have the same length and direction, and represent the same quantity (such as force or velocity).Draw several equal vectors.
11Inverse VectorsInverse vectors have the same length, but opposite direction.Draw a set of inverse vectors.A-A
16Sample problemA surveyor stands on a riverbank directly across the river from a tree on the opposite bank. She then walks 100 m downstream, and determines that the angle from her new position to the tree on the opposite bank is 50o. How wide is the river, and how far is she from the tree in her new location?
17Sample problemA surveyor stands on a riverbank directly across the river from a tree on the opposite bank. She then walks 100 m downstream, and determines that the angle from her new position to the tree on the opposite bank is 50o. How wide is the river, and how far is she from the tree in her new location?
18Sample problemYou are standing at the very top of a tower and notice that in order to see a manhole cover on the ground 50 meters from the base of the tower, you must look down at an angle 75o below the horizontal. If you are 1.80 m tall, how high is the tower?
19Sample problemYou are standing at the very top of a tower and notice that in order to see a manhole cover on the ground 50 meters from the base of the tower, you must look down at an angle 75o below the horizontal. If you are 1.80 m tall, how high is the tower?
20Vectors: x-component A Ax The x-component of a vector is the “shadow” it casts on the x-axis.cos θ = adjacent ∕ hypotenusecos θ = Ax ∕ AAx = A cos AxAx
21Vectors: y-componentThe y-component of a vector is the “shadow” it casts on the y-axis.sin θ = opposite ∕ hypotenusesin θ = Ay ∕ AAy = A sin yAAyAyx
22Vectors: angleThe angle a vector makes with the x-axis can be determined by the components.It is calculated by the inverse tangent function = tan-1 (Ay/Ax)yRyxRx
23R Vectors: magnitude Ry Rx The magnitude of a vector can be determined by the components.It is calculated using the Pythagorean Theorem.R2 = Rx2 + Ry2yRRyxRx
24Conceptual Practice Problem Can the magnitude of a component of a vector be greater than the vector’s magnitude?Explain…
25Practice ProblemYou are driving up a long inclined road. After 1.5 miles you notice that signs along the roadside indicate that your elevation has increased by 520 feet.What is the angle of the road above the horizontal?How far do you have to drive to gain an additional 150 feet of elevation?
26Practice Problem Find the x- and y-components of the following vectors R = ov = oa = o
27Practice ProblemsA water molecule is shown in the diagram. The distance from the center of the oxygen atom to the center of the hydrogen atom is 0.96 angstroms, and the angle between the hydrogen atoms is 104.5°.Find the center-to-center distance between the hydrogen atoms.0.96 Ǻ104.5°
28Graphical addition and subtraction VectorsGraphical addition and subtraction
29Graphical Addition of Vectors Add vectors A and B graphically by drawing them together in a head to tail arrangement.Draw vector A first, and then draw vector B such that its tail is on the head of vector A.Then draw the sum, or resultant vector, by drawing a vector from the tail of A to the head of B.Measure the magnitude and direction of the resultant vector.
30Practice Graphical Addition BABRA + B = RR is called the resultant vector!
31The Resultant and the Equilibrant The sum of two or more vectors is called the resultant vector.The resultant vector can replace the vectors from which it is derived.The resultant is completely canceled out by adding it to its inverse, which is called the equilibrant.
32The Equilibrant Vector A + B = RThe vector -R is called the equilibrant.If you add R and -R you get a null (or zero) vector.
33Graphical Subtraction of Vectors Subtract vectors A and B graphically by adding vector A with the inverse of vector B (-B).First draw vector A, then draw -B such that its tail is on the head of vector A.The difference is the vector drawn from the tail of vector A to the head of -B.
35Practice ProblemVector A points in the +x direction and has a magnitude of 75 m. Vector B has a magnitude of 30 m and has a direction of 30o relative to the x axis. Vector C has a magnitude of 50 m and points in a direction of -60o relative to the x axis.Find A + BFind A + B + CFind A – B.
39Component addition and subtraction VectorsComponent addition and subtraction
40Component Addition of Vectors Resolve each vector into its x- and y-components.Ax = Acos Ay = AsinBx = Bcos By = BsinCx = Ccos Cy = Csin etc.Add the x-components (Ax, Bx, etc.) together to get Rx and the y-components (Ay, By, etc.) to get Ry.
41Component Addition of Vectors Calculate the magnitude of the resultant with the Pythagorean Theorem (R = Rx2 + Ry2).Determine the angle with the equation = tan-1 Ry/Rx.
42Practice ProblemIn a daily prowl through the neighborhood, a cat makes a displacement of 120 m due north, followed by a displacement of 72 m due west. Find the magnitude and displacement required if the cat is to return home.
43Practice ProblemIf the cat in the previous problem takes 45 minutes to complete the first displacement and 17 minutes to complete the second displacement, what is the magnitude and direction of its average velocity during this 62-minute period of time?
44Relative Motion September 2013 VectorsRelative MotionSeptember 2013
45Relative MotionRelative motion problems are difficult to do unless one applies vector addition concepts.Define a vector for a swimmer’s velocity relative to the water, and another vector for the velocity of the water relative to the ground. Adding those two vectors will give you the velocity of the swimmer relative to the ground.
49Practice ProblemYou are paddling a canoe in a river that is flowing at 4.0 mph east. You are capable of paddling at 5.0 mph.If you paddle east, what is your velocity relative to the shore?If you paddle west, what is your velocity relative to the shore?You want to paddle straight across the river, from the south to the north.At what angle to you aim your boat relative to the shore? Assume east is 0o.
50Practice ProblemYou are flying a plane with an airspeed of 400 mph. If you are flying in a region with a 80 mph west wind, what must your heading be to fly due north?