Angular acceleration and velocity in a circle

In summary, the turntable slows down from 33.33 RPM to a stop at a constant rotational acceleration of -0.164 rad/s^2 over a period of 21 seconds. This results in a final angular velocity of 1.81 rad/s and a final linear velocity of 0.276 m/s in the North direction. The linear acceleration is 25E-3 m/s^2 in the South direction and the centripetal acceleration is 0.5 m/s^2 in the West direction.
  • #1
ac7597
126
6
Homework Statement
Use the following words to describe directions: "North", "South", "East", "West", "Up", and "Down"
Adam sits on the outer edge of a vinyl record, which has a radius R=6 inches. The record spins on a turntable at 33.33 RPM in a counterclockwise direction as seen from above. Adam loves going around in circles.
Alas, the record finishes playing, and the motor disengages. Over the next 21 seconds, the record gradually slows to a halt. You may assume that the angular acceleration is constant.

At time t=10 seconds after the motor disengages, Adam happens to be located directly East of the spindle. At this instant:
What is Adam's angular velocity? Give the magnitude and the direction.

What is Adam's linear velocity at this moment? Also give the direction (North, South, East, West)

What is Adam's angular acceleration at this moment? Just provide the magnitude.

What is the tangential linear acceleration of Adam? That is, what is the rate of change of his linear speed? You should be able to provide a direction this time.

What is Adam's centripetal acceleration at this moment?
Relevant Equations
angular velocity=initial angular velocity + angular acceleration(time)
radius=6in=0.1524m
33.33 RPM (1min/60second)(6.28 radian/1 revolution) = 3.45 rad/s
linear velocity=3.45 rad/s * 0.1524m=0.526 m/s
linear acceleration= (0.526 m/s)^2 /(0.1524m)=1.814 m/s^2
1.814 m/s^2=(0.1524m)(rotational acceleration)
rotational acceleration=11.9 rad/s^2

ω1= (3.45 rad/s)+(11.9rad/s^2)(10s)
ω1=122.4 rad/s Up
 
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  • #2
You seem to have confused rotational acceleration with centripetal acceleration. The problem states that the turntable slows to a stop at a constant rotational acceleration from 33RPM over 21 seconds. You can use that information and this equation to calculate the rotational acceleration:
ac7597 said:
Homework Equations: angular velocity=initial angular velocity + angular acceleration(time)
 
  • #3
0=3.45 + (rotational acceleration)(21s)
rotational acceleration= -0.164 rad/s^2
|rotational acceleration|= 0.164 rad/s^2

ω1= (3.45 rad/s)+(-0.164 rad/s^2)(10s)
ω1= 1.81 rad/s Up

linear velocity = 1.81 rad/s * 0.1524m = 0.276 m/s North

linear acceleration = 0.164 rad/s^2 * 0.1524m= 25E-3m/s^2 South

centripetal acceleration= (0.276 m/s)^2 / 0.1524m=0.5m/s^2 West
 
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1. What is angular acceleration?

Angular acceleration is the rate of change of angular velocity with respect to time. In simpler terms, it is how quickly an object's rotational speed changes over time.

2. How is angular acceleration different from linear acceleration?

Linear acceleration is the rate of change of linear velocity, while angular acceleration is the rate of change of angular velocity. Linear acceleration describes changes in an object's straight-line motion, while angular acceleration describes changes in an object's rotational motion.

3. How is angular velocity related to angular acceleration?

Angular velocity and angular acceleration are directly related. Angular acceleration is the derivative of angular velocity, meaning it describes the change in angular velocity over time. In other words, angular acceleration tells us how much the angular velocity is increasing or decreasing.

4. Can an object have constant angular acceleration?

Yes, an object can have constant angular acceleration if its angular velocity increases or decreases at a constant rate. This means that its angular acceleration remains the same throughout the motion.

5. How is angular acceleration and velocity affected by the radius of the circle?

The radius of the circle does not directly affect angular acceleration and velocity. However, it does have an impact on the linear speed of the object. As the radius of the circle increases, the linear speed of the object also increases, while the angular velocity remains the same. This means that the object is covering a greater distance in the same amount of time, resulting in a higher linear speed.

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