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Racing disks. The figure shows two disks that can rotate about their centers lik

ID: 1309049 • Letter: R

Question

Racing disks. The figure shows two disks that can rotate about their centers like a merry-go-round. At time t = 0, the reference lines of the two disks have the same orientation. Disk A is already rotating, with a constant angular velocity A. Disk B has been stationary but now begins to rotate at a constant angular acceleration B. What is the first time t after t = 0 that the reference lines of the two disks momentarily have the same angular displacement? State your answers in terms of the given variables.

Explanation / Answer

EXAMPLE

two disks that can rotate about their centres like a merry-go-round. At time t = 0, the reference lines of the two disks have the same orientation. Disk A is already rotating, with a constant angular velocity of 9.5 rad/s. Disk B has been stationary but now begins to rotate at a constant angular acceleration of 2.2 rad/s2. (a) At what time t will the reference lines of the two disks momentarily have the same angular displacement ? ? (b) Will that time t be the first time since t = 0 that the reference lines are momentarily aligned?

The equations of motion for the angular displacement of each disk are given by:

Disk A: R1(t) = (1/2)*alpha1*t