Engineering 312 Engineering Graphics Fall 2013
Assignment 6
Coordinate Systems and Vector Analysis
Due: Wednesday 18 September 2013
Create the following AutoSketch drawings. Put a border and title block on each drawing. Print and assemble them into a packet with a cover page and staple.
Entering Coordinates
Often you can use grid snap to draw lines. For other lines you will have to locate the points another kind of snap or by entering coordinates. There are lots of kinds of snaps on the toolbar. Typing R will bring up the “Enter 2D Coordinate” dialog box.
Move the Origin
For this exercise, using absolute coordinates is easier if you move the origin to 0.75”, 0.75” in tools/drawing options/scale.
Help With Angles
Since all angles in AutoSketch are measured counter-clockwise from a line going to the right, you will have to calculate the angles to enter. You can get a little help with figuring out angles if you turn off snap, then set up the status bar to display the angle. Start a line, then wiggle the mouse around and watch how the angle changes in the status bar.
To do this, right click the status bar, select properties, click the Polar button, Check: Display Relative Coordinates
Check: Display Absolute Coordinates
UNcheck: Automatically Update to Match Grid and Ruler
1) Drawing 1: Use Table 4-3 to draw the figure using absolute rectangular coordinates. Each point is referenced from the origin. You will basically be plotting out points and connecting the dots. “New Start” means to pick up your pencil (do not draw a line between these points). The drawing will fit on an A size inch paper if you do it right.
2) Drawing 2: Use the Table 4-5 to draw the figure using relative rectangular coordinates. Each point is located relative to the point before it. Use an A-size metric paper.
3) Drawing 3: Draw Figure 4-33. This is really an exercise in using relative polar coordinates. Each point is located relative to the point before it, using an angle and a length. Draw the figure, but do draw dimensions.
Vector Addition
A vector is a line with a magnitude and a direction that represents some quantity such as force, distance, velocity, acceleration, etc. Vector analysis is used by engineers to determine unknown resultant quantities given some known quantities. You will learn more about vector analysis in your math and physics courses. One common graphical vector analysis method is called “vector addition”. In vector addition we draw the vectors Tail-to-Tip from which we can determine the resultant vector. For example, given the following vectors:
V1 = 1.5D35
V2 = 2.5D120
V3 = 7.5D5
We can draw a figure (shown) to determine the resultant vector, VR = 8.31D26.28
4) Drawing 4: Add the following vectors by drawing them Tail-to-Tip. Draw the resultant vector. Label all vectors as shown in the previous example.
V1 = 0.5D45
V2 = 5.2D60
V3 = 6.5D355
5) Drawing 5: The British have a game called “Rugby”. Although rugby has no rules whatsoever, vector analysis can still be applied! Consider a huddle in rugby, where 5 players are all trying to push the ball in different directions. Use vector addition to determine the direction the ball-huddle unit will move. Add the following vectors by drawing them Tail-to-Tip. Draw the resultant vector. Label all vectors as shown in the previous example.
V1 = 2.22D180
V2 = 2.73D270
V3 = 3.12D20
V3 = 2.55D70
V3 = 3.42D90
6) Drawing 6: “Will it fly?” In fluid mechanics, “Bernouli’s Principle” tells us that pressure decreases as velocity increases. Airfoils utilize this principle to generate lift. Go to www.flc.losrios.edu/~ross and find the file “wing vector.skf”. To determine the resultant lift vector, use the translate command with endpoint snap to arrange all the force vectors tail-to-tip. Modify the supplied drawing as necessary to show the final solution, and label the magnitude and direction of the resultant lift vector. Will it fly?
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