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DEFINITIONS: Define the following terms.

Force (F) - a physical quantity that can affect the motion of an object.

Mass (m) - A measure of the amount of material.

Pressure (p) - The force applied over a unit area.

Velocity (V) - Speed (distance per time) in a particular direction.

Density (r) - Mass per unit volume.

UNIT ANALYSIS:  Complete the table giving the correct unit of measurement in both the English and the Metric systems. You will use this information when solving the problems shown below.

QUANTITY
ENGLISH UNIT
METRIC UNIT

LENGTH

feet

meter

AREA

square feet

square meter

VOLUME

cubic feet

cubic meter

FORCE

pounds

Newtons

MASS

slug

kilograms

PRESSURE

pound/square feet

Newtons/square meter

VELOCITY

feet/second

meter/second

DENSITY

slug/cubic feet

kilograms/cubic meter

PROBLEMS: Solve each problem. Make sure all units agree!!

1. Find the total air pressure detected by the pitot tube for a Cessna 182 airplane flying at a pressure altitude of 10,000 feet (static pressure of 1455.6 lb/ft2 ) and a speed of 120 knots if the air density is 0.00162 slugs/ft3?
pt = 1455.6 lb/sq ft + [(0.00162 sl/cu ft) (120 kts x 1.69 ft/s/kt)/2] = 1489 lb/sq ft

2. Find the difference in pressure (pt-ps) for the same conditions described above if the airplane speeds up to 160 knots.
pt-ps = [(0.00162 sl/cu ft)(160 kts x 1.69 ft/s/kt)2] /2 = 59.22 lb/sq ft

3. If the total air pressure for the same Cessna 182 is measured at 1478.7 lb/ft2, what is the new velocity in knots of the airplane?
V = [2(1478.7 lb/sq ft - 1455.6 lb/sq ft)/0.00162 sl/cu ft]1/2 = 169 ft/sec/1.69 ft/sec/kt = 100 kts

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