school
posted by Aaron .
Two disks are spinning freely about axes that run through their respective centres (see figure below). The larger disk
(R1 = 1.42 m)
has a moment of inertia of 1180 kg · m2 and an angular speed of 4.0 rad/s. The smaller disk
(R2 = 0.60 m)
has a moment of inertia of 906 kg · m2 and an angular speed of 8.0 rad/s. The smaller disk is rotating in a direction that is opposite to the larger disk. The edges of the two disks are brought into contact with each other while keeping their axes parallel. They initially slip against each other until the friction between the two disks eventually stops the slipping. How much energy is lost to friction? (Assume that the disks continue to spin after the disks stop slipping.)

The initial angular momentum of disc 1
is I1 w1
The initial angular momentum of disc 2
is I2 w2
Add those for total angular momentum, which DOES NOT CHANGE in this problem
because there are no external moments
Afterwards the no slip condition:
R1 w1 = R2 W2
calculate the angular momentum again and find new w s
Now
Initial KE = (1/2) I1 w1^2+(1/2)I2 w2^2
Final Ke = same formula, new w s
final better be less than initial :)
find difference
Respond to this Question
Similar Questions

Physics
Two disks are rotating about the same axis. Disk A has a moment of inertia of 4.53 kg·m2 and an angular velocity of +4.55 rad/s. Disk B is rotating with an angular velocity of 6.86 rad/s. The two disks are then linked together without … 
physics
Two disks are rotating about the same axis. Disk A has a moment of inertia of 3.7 kg · m2 and an angular velocity of +7.3 rad/s. Disk B is rotating with an angular velocity of 9.5 rad/s. The two disks are then linked together without … 
physics
There are two spinning disks A and B arranged so that they initially are separated but can be pushed into contact. Disk A is made of a lighter material, so it has a moment of inertia that is one third that of disk B. Disk A starts … 
Physics
Two disks are rotating about the same axis. Disk A has a moment of inertia of 3.8 kg · m2 and an angular velocity of +6.7 rad/s. Disk B is rotating with an angular velocity of 8.9 rad/s. The two disks are then linked together without … 
Physics (help)
A solid disk 1 with radius R1 is spinning freely about a frictionless horizontal axle l at an angular speed ω initially. The axle l is perpendicular to disk 1, and goes through the center S of disk 1. The circumference of disk … 
Physics Classical Mechanics
A solid disk 1 with radius R1 is spinning freely about a frictionless horizontal axle l at an angular speed ω initially. The axle l is perpendicular to disk 1, and goes through the center S of disk 1. The circumference of disk … 
Physics
Consider the rods plus disc system shown in the Figure. The rod has a length L =0.50 m, and mass M = 0.270kg. The large disc has a radius of R = 0.130m and mass m=0.810kg. The second disk should be treated as a point mass of 0.405kg. … 
Physics
Two disks are rotating about the same axis. Disk A has a moment of inertia of 3.1 kg · m2 and an angular velocity of +8.0 rad/s. Disk B is rotating with an angular velocity of 10.2 rad/s. The two disks are then linked together without … 
physics
A disk of mass m is spinning freely at 6.22 rad/s when a second disk of identical mass, initially not spinning, is dropped on it so that their axes coincide. In a short time the two disks are corotating. (The two disks have the same … 
physics
Two disks are rotating about the same axis. Disk A has a moment of inertia of 3.6 kg · m2 and an angular velocity of +7.9 rad/s. Disk B is rotating with an angular velocity of 10.6 rad/s. The two disks are then linked together without …