Question

Dario, a prep cook at an Italian restaurant, spins a salad spinner and observes that it rotates 20.0 times in 5.00 seconds and then stops spinning it. The salad spinner rotates 6.00 more times before it comes to rest. Assume that the spinner slows down with constant angular acceleration. What is the magnitude of the angular acceleration of the salad spinner as it slows down??

Answer #1

**Given**

**20 rev in 5 seconds**

**that is the angular velocity w = 20 /5 = 4 rev/s = 4*2pi
rad/s = 8pirad/s**

**the displacemnt is theta = 20*2pi rad = 40 pi
rad**

**the angular velocity is w1 = theta1/t = 40 pi /5 =
25.133 rad/s**

**and making 6 more rotations before come to
rest**

**the displacement covered in 6 rotations is theta2 =
6*2pi = 12*pi rad = 37.7 rad**

**from equations of motion **

**w2^2 -w1^2 = 2*alpha(theta)**

**here W2 = 0 rad/s comes to rest**

**alpha = -W1^2/(2(theta2))**

**alpha = -(25.133)^2/(2(37.7) rad/s2**

**alpha = -8.378 rad/s2**

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Assessment
Identify the Variables!
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