Physics problems 1) A regular CD player spins a CD as fast as 500 rpm. Given tha
ID: 1371658 • Letter: P
Question
Physics problems
1) A regular CD player spins a CD as fast as 500 rpm. Given that the mass of a CD is about 16 grams, estimate the rotational kinetic energy of a CD spinning at max speed in a regular CD player (as always, you may have to estimate/measure other physical quantities to get an answer). Explain, mostly in words, rather than equations, how you got your result.
2) A book can be rotated about many different axes. The moment of inertia of the book will depend upon the axis chosen. Using the image shown, rank the axes shown in red (A, B and C) from largest to smallest moment of inertia (a.k.a. rotational inertia) around that axis.
Explanation / Answer
given,
speed = 500 rpm or 52.3598 rad/sec
mass = 16 gm
moment of inertia = 0.5 * m * r^2
moment of inertia = 0.5 * 16 * 10^-3 * r^2
rotational kinetic energy = 0.5 * I * w^2
rotational kinetic energy = 0.5 * 0.5 * 16 * 10^-3 * r^2 * 52.3958^2
rotational kinetic energy = 10.981 * r^2 J