Physics quiz question: basketball vs. tennis ball angular speed

Physics 205A Quiz 5, fall semester 2018
Cuesta College, San Luis Obispo, CA

A basketball (mass 0.43 kg, radius 0.11 m) and a tennis ball (mass 0.058 kg, radius 0.033 m) 
both roll without slipping across a horizontal floor with the same constant speed of 0.50 m/s.

Both objects are hollow spheres (I = (2/3)·M·R²).

As they roll across the floor, the __________ has a faster angular speed.
(A) basketball.
(B) tennis ball.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (B)

The relationship between the translational speed v and angular speed ω for objects that roll without slipping is given by:

v = r·ω,

and since both objects have the same translational speed of 0.50 m/s, then the object with the smaller radius r (the tennis ball) will have the faster angular speed ω.

Sections 70854, 70855
Exam code: quiz05Ro74
(A) : 8 students
(B) : 28 students
(C) : 16 students
(D) : 0 students

Success level: 54%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.88