SIFT flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Rotation vs. reflection
- A rotated drawing keeps the same shape and handedness; a reflected drawing is a mirror image and is not identical, even if its outline looks similar.
- Counting line segments
- Matching drawings must have the same number of line segments and endpoints; an extra, missing, or shortened segment makes an option incorrect.
- Angle sequence check
- Compare the order of acute, right, and obtuse angles around the figure; a mismatch in any angle rules out that answer choice.
- Proportion preservation
- Identical drawings may be moved or turned but not stretched; compare relative lengths of paired sides to reject distorted choices.
- First-mismatch elimination
- Scan each option for one clear difference from the target, such as a mirrored corner or changed intersection, then eliminate it without further checking.
- Distinctive feature search
- Find the target figure inside a complex pattern by first locating its most unusual angle, parallel pair, or closed region, rather than searching for the whole outline.
- Line continuation
- Follow straight lines through crossing points in a complex drawing; the embedded target's sides often continue through intersections and can be traced as one straight segment.
- Vertex counting
- A hidden polygon with n sides must appear with n vertices and n sides; count potential vertices to confirm or reject a suspected embedded shape.
- Shared-side hiding
- A target figure may share one or more sides with a larger surrounding shape, so extra lines inside or outside the target do not disqualify that region.
- Cyclic control
- The cyclic stick changes the tilt of the main rotor disc, controlling pitch attitude and roll; moving it forward noses the helicopter down and increases forward airspeed.
- Collective control
- The collective lever changes main rotor blade pitch collectively, increasing or decreasing lift and power required; raising it generally makes the helicopter climb.
- Translational lift
- As a helicopter gains forward airspeed, it moves out of its own downwash and into cleaner air, increasing rotor efficiency and lift without extra power.
- Autorotation
- After engine failure, autorotation uses upward airflow through the rotor to keep blades turning; the pilot manages descent rate and flares before landing.
- Ground effect
- Close to the ground, usually within about one rotor diameter, downwash is restricted, induced airflow decreases, and less power is needed to hover.
- Attitude indicator colors
- On a standard attitude indicator, blue represents sky and brown represents ground; the boundary between them is the horizon line used to judge pitch and bank.
- Heading indicator cardinal points
- A heading indicator reads 0 or 360 for north, 90 for east, 180 for south, and 270 for west; the selected outside view should face the indicated heading.
- Standard-rate turn
- A standard-rate turn changes heading at about three degrees per second, so a 180-degree turn takes about 60 seconds and a 90-degree turn about 30 seconds.
- Coordinated turn ball
- In a turn coordinator or inclinometer, the ball centered means the turn is coordinated; a ball outside the center indicates slipping or skidding.
- Nose-up indication
- On a typical attitude indicator with a fixed aircraft symbol, a nose-up attitude moves the horizon bar downward relative to the symbol; nose-down moves it upward.
- Main idea
- The main idea is the central point the passage supports throughout; it is broader than a single detail and should cover the whole text.
- Inference
- An inference is a conclusion logically supported by the passage but not stated directly; it must follow from the text, not from outside knowledge.
- EXCEPT questions
- For a question asking which statement is NOT supported, test each choice against the passage and eliminate the ones the text directly supports.
- Tone words
- Author tone is revealed by word choice; neutral, critical, optimistic, and objective are common tones, and extreme language often signals a biased or emotional tone.
- Percent change formula
- Percent change equals the amount of change divided by the original value, multiplied by 100; a positive result is an increase and a negative result a decrease.
- Weighted average
- A weighted average multiplies each value by its weight, adds the products, and divides by the total weight; it differs from a simple average when weights are unequal.
- Distance formula
- Distance traveled equals rate multiplied by time, or d = rt; rearrange to r = d/t or t = d/r when solving for speed or time.
- Pythagorean theorem
- In a right triangle, the square of the hypotenuse equals the sum of the squares of the legs: a squared plus b squared equals c squared.
- Work-rate shortcut
- For two workers, add their rates as fractions of the job per unit time, then take the reciprocal of the sum to find the combined time to finish.
- Lever equilibrium
- A lever balances when the effort force times its distance from the fulcrum equals the load force times its distance from the fulcrum, ignoring friction.
- Gear ratio
- Gear ratio equals the number of teeth on the driven gear divided by teeth on the driving gear; meshed external gears rotate in opposite directions.
- Mechanical advantage
- Mechanical advantage is the output force divided by the input force, or the input distance divided by the output distance for an ideal simple machine.
- Ohm's law
- Ohm's law states voltage equals current multiplied by resistance, V = IR; it applies to simple resistive circuits and can be rearranged for current or resistance.