Question

A disk is initially rotating (about its center) at 48 rad/s counter-clockwise. After a constant angular acceleration is applied to it for 2.2 seconds, it is rotating at 9 rad/s counter-clockwise. How many revolutions does the disk make in that time

Answer 1

From the given question,

Initial angular speed($\omega _{1}$)=48 rad/s

time(t)=2.2 sec

Final angular speed($\omega _{2}$)=9 rad/s

average anguar speed= (48+9)/2= 28.5 rad/s

angular displacement= 28.5 x 2.2=62.7 rad

2$\pi$ radians = 1 revolution

62.7 rad= (62.7/2$\pi$)=9.979 revolutions

=10 revolutions(approx)