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UNIT ANALYSIS: In the table provided, give the correct units in both the English and the Metric systems.

QUANTITY
ENGLISH UNIT
METRIC UNIT

time

seconds

seconds

distance

feet

meters

mass

slug

kilogram

force

pounds

Newtons

velocity

feet/second

meters/second

acceleration

feet/second squared

meters/second squared

PROBLEMS: Solve the following problems and show your work in the space provided. (Don't forget to label your answer with the proper units.)

1. An airplane begins its takeoff run at a speed of 40 knots. If the runway is 6,000 ft long and it takes 20 seconds to reach liftoff speed, what acceleration must the pilot maintain for takeoff? (One Knot=1.69 ft/sec)
6,000 ft = a(20 sec)2/2 + [(40 kts x 1.69 ft/sec/kts)(20 sec)] a = 23 ft/sec

2. An 8,200 kg airplane touched its runway at 65 m/s and came to a stop in 25 seconds.
Find
(A) negative acceleration
0 = a(25 sec) + 65 m/s a = -2.6 m/ sq s

(B) the length of the runway
X - X0 = (-2.6 m/sq s)(25 sec)/2 + 65 m/s (25 sec) = 1592.5 m

3. A 9,600 lb airplane takes off at 160 ft/sec. If it accelerates at a constant rate of 30 ft/sec2:
1. How much time is needed to reach takeoff speed?
160 m/s = (30 ft/sq sec)t + 0m/s t=5.3 sec
2. What length airstrip is used?
X - X0 = (30 ft/sq sec)(5.3 sec) = 80 ft
3. What force is needed to produce this acceleration?
F = (9600 lbs/32.2 ft/sl)(30 ft/ sq sec) = 8944 lbs

4. A military airplane flying at a speed of 350 m/s must make a supply drop. The pilot releases the supply crate 2,400 m before the drop target. How long will it take for the crate to hit the ground?
0 = (9.8 m/sq s)t/2 + (350 m/s) + 2,400 m
t = 6.22 sec (by the quadratic equation)

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