In this Investigation you will be studying the conservation of angular momentum.
ID: 3281455 • Letter: I
Question
In this Investigation you will be studying the conservation of angular momentum. Unfortunately, with our rotational dynamic apparatus we can not detect the direction of the rotation of the disk. If a disk rotates with the same magnitude of angular speed clock- or counter-clockwise our data acquisition system will always display it as a positive number.
With that caveat in mind consider the following scenarios.
(a) At first the top disk spinning and the bottom disk stationary and then the top disk drops onto the bottom one and they stick together.
(b) At first the top and bottom disks spinning in the same direction but at different rates and then the top disk drops onto the bottom one and they stick together.
(c) At first the top and bottom disks spinning in opposite directions at different rates and then the top disk drops onto the bottom one and they stick together.
(d) At first the top and bottom disks spinning in opposite directions at the same rate and then the top disk drops onto the bottom one and they stick together.
Match scenarios (a), (b), (c), and (d) with corresponding graphs of disks' angular velocity vs. time displayed below.
Explanation / Answer
a. graph 1,
one disc is moving in +ve direction while the other is rotating in -ve direction, hence two angular speed graphs in +ve axis
so when they combine the net speed becomes lesser in magnitude as compared to the rotational velocity magnitude of both
hence
(c) At first the top and bottom disks spinning in opposite directions at different rates and then the top disk drops onto the bottom one and they stick together.
b. graph 2.
her one disc is at rest, the otehr one is rotating and when they stic they rotate together with half the initial angular speed
(a) At first the top disk spinning and the bottom disk stationary and then the top disk drops onto the bottom one and they stick together.
c. graph 3. one disc is moving really fast, other is really slow, and both get stuck and move at an average speed closer to the slower moving disc.
(b) At first the top and bottom disks spinning in the same direction but at different rates and then the top disk drops onto the bottom one and they stick together.
d. both discs are moving at same rates but final speed is 0, hence originally they were moving in opposite directions
(d) At first the top and bottom disks spinning in opposite directions at the same rate and then the top disk drops onto the bottom one and they stick together.