Physics 205A Quiz 4, Spring Semester 2009
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 6.22
[3.0 points.] An injured fruit bat (mass 0.60 kg) that latched onto the external fuel tank of the NASA Space Shuttle was presumed to have been carried along during a recent liftoff[1]. How much energy was expended by having to lift the bat from rest to a speed of 7.8 km/s (when the fuel tank is separated[2])?
(A) 2.3e+03 J.
(B) 4.7e+03 J.
(C) 1.8e+07 J.
(D) 3.7e+07 J.
Correct answer: (C)
The energy expended (work done) is given by:
W = delta(K_tr) = (1/2)*m*(v_f^2 - v_i^2),
where v_i = 0. Response (A) is (1/2)*m*v_f; response (B) is m*v_f (the final momentum of the bat); while response (C) is m*v_f^2.
Student responses
Sections 30880, 30881
(A) : 10 students
(B) : 7 students
(C) : 26 students
(D) : 0 students
Footnotes:
[1] "NASA—Bat Hung onto Shuttle During Liftoff," www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts119/launchbat.html
[2] "17,440 mph," spaceflight.nasa.gov/shuttle/reference/basics/index.html
"Difficulty level": 60%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.34
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