Physics quiz question: basketball horizontal velocity component

Physics 205A Quiz 3, fall semester 2018
Cuesta College, San Luis Obispo, CA

A Physics 205A student throws a basketball with an initial velocity vector that has x- and y-components:

v_0x = +5.5 m/s,
v_0y = +4.2 m/s.

Neglect air resistance. At the highest point in its trajectory, the magnitude of the basketball's horizontal velocity is:
(A) 0 m/s.
(B) some value between 0 m/s and 5.5 m/s.
(C) 5.5 m/s.
(D) some value greater than 5.5 m/s.

Correct answer (highlight to unhide): (C)

For the ideal case of projectile motion where air resistance is negligible, the vertical component of the ball's velocity continuously changes (due to the downwards vertical acceleration due to gravity), while the horizontal component of the ball's velocity remains constant (due to there being no horizontal acceleration).

Sections 70854, 70855
Exam code: quiz03pRH5
(A) : 3 students
(B) : 8 students
(C) : 38 students
(D) : 6 students

Success level: 68%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.73