Cuesta College, San Luis Obispo, CA
The following case study was reported on a collision law firm website:
Richard and his wife were [in] the last of a line of cars stopped for a red light. The vehicle behind Richard's didn't stop and rammed his car while going [approximately 10 m/s]. Richard's car was damaged on the rear, and it cost almost $6,000 to repair the damage.Assume that both cars were stuck together after this accident. Ignore friction, drag, and external forces during this brief collision. Based solely on the (original and additional) information given for this collision, __________ must have been conserved.
(A) translational kinetic energy.
(B) momentum.
(C) (Both of the above choices.)
(D) (Neither of the above choices.)
[*] all-about-car-accidents.com/resources/accidents/car-accidents/examples-rear-end-car-accid.
Correct answer: (B)
Negligible net external force and brief time duration for this collision makes the external impulse on this system zero, such that momentum is conserved. Since both cars are stuck together after the collision, some translational kinetic energy was irreversibly lost in deformation, such that it is not conserved for this completely inelastic collision.
Sections 70854, 70855
Exam code: quiz04w33N
(A) : 6 students
(B) : 31 students
(C) : 4 students
(D) : 7 students
Success level: 65%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.26
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