Question 1 Answers

1) ( )( ) ( )

F = 4,646 N

2) ( ) ( )

( ) ( )

( )

⁄

( ) ( )

√ ( )

( )

𝑉 𝑚⁄𝑠

3)

@engine: 398,148W

4) A) No; mass flow wasted to keep rider up.

B) – Volume output of pump

— max pressure of pump

—drag force @ boat @ speed

— rider weight

Question 2: Aircraft Aerodynamics (25 points)

A small commercial airplane weighing 20,000 lbs flies at a cruising attitude of 33,000 feet. The ambient

air density is 7.9656 X 10 slug/ft3. The wing surface area is 450 ft2.

a) Draw a free body diagram of all of the forces acting on the airliner at cruising speed. What is the

lift force.

= 533Hp

W

Points

1 5 — 2 not count 0, 9 — 1 each random

2 9

3 6

4 a) 2 b) 3

— 3 for slower — 1 miscale A — 1 random

— 3 for V1 — 2 for V2 — 1 random — 1 don’t count

— anything reasonable

— 1 each

x0

3x

T Vc

L

W

D

L=W When cruising because it is in steady flight.

b) Which of the following would be a reasonable lift/drag ratio? Select one value, then calculate

the forward thrust of the airplane.

Select a L/D ratio:

1/200 1/20 1

c) Given the L/D ratio selected in part b, we would like to dete

200

rmine the stall velocity of the

airplane. Assume CD = 0.015 as the airplane enters stall.

20.

( ) √ √

( ⁄ )( )( )

⁄

20

Image by MIT OpenCourseWare.

Question 3: Signal Processing (20 points)

The base signal in Figure 1 is modulated using Double-sideband suppressed-carrier transmission (DSB-

SC), the result of which is shown in Figure 1. In order to interpret the signal on the receiver end, we

perform a Fourier transform of the incoming data, with the output shown in figure 2.

Identify the carrier frequency and the frequency components of the base band signal.

Carrier Signal (Hz)

𝐹𝐶 𝐻𝑧

(According to FFT plot)

Base Band Signal (Hz)

(Use as many frequencies as

needed to fully describe the signal)

𝐹𝐵 1000 Hz

𝐹𝐵 1500 Hz

𝐹𝐵 -

𝐹𝐵 -

Image by MIT OpenCourseWare.

2) By re-using the heat from the exhaust gases to pre-heat the compressed intake air, reducing the

amount of fuel needed to be burned for the heat-addition to the Brayton cycle .

3) Three. More satellites would allow for averaging of the time-stamp signal and greater accuracy

due to correction for the satellite reference time drift.

4) Based on the design speed of the aircraft. Turbofans can attain lower engine outlet velocities at

higher mass-flow rates, allowing for more efficient propulsion at lower speed.

5) Angle of Attack

1)

4

Figure 1

Stable Unstable

r2

M2

G

B

r1

FG1

FB1

M1

G

B

Figure 2

Boat A Boat B

Moment Acting on Ship A =

Moment Acting on Ship B =

G

B

G

B

aa

FB1 = FG1

-FB1r1 = -(FB1+FG1) r1

2 = -FB1r1

FB2r2 = (FB2+FG2) r2

2 = FB2r2

Question 4 Answers

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16.682 Technology in TransportationSpring 2011

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