# Angular Accerlation Homework: Avg. Angular Acc in Rad/s2

• cstout
In summary, the question asks for the average angular acceleration of a computer's hard disk, which spins at 7200 rpm during normal operation. The hard disk takes 3.7 seconds to reach this angular velocity from rest. Using the equation \alpha=\frac{\Delta \omega}{\Delta t}, the answer is not accepted by the online homework system and it is unclear where the mistake was made.
cstout

## Homework Statement

During normal operation, a computer's hard disk spins at 7200 rpm. If it takes the hard disk 3.7 s to reach this angular velocity starting from rest, what is the average angular acceleration of the hard disk in rad/s2?

## Homework Equations

Change in Angular Accerlation/ Change in time

## The Attempt at a Solution

I tried the above equation but the online homework says the answer is wrong. I'm not sure of what else to do.

If you don't show your work, how can we know where you went wrong?

Also, your equation given is not an equation (there is no equal sign), but either way, change in acceleration/change in time is a rate of change of acceleration, which would not help you here. Did you mean this?

$$\alpha=\frac{\Delta \omega}{\Delta t}$$

Hello,

Thank you for reaching out with your question about angular acceleration. Based on the information provided, it seems like you are on the right track with your attempt at using the equation for average angular acceleration. However, it is important to note that the units for angular acceleration are typically in radians per second squared (rad/s^2).

In this case, the hard disk is spinning at a rate of 7200 rpm (revolutions per minute), which can be converted to radians per second by multiplying by 2π/60 (since there are 2π radians in one revolution and 60 seconds in one minute). This gives us an angular velocity of 754.38 rad/s.

To find the average angular acceleration, we can use the equation:

Average angular acceleration = (final angular velocity - initial angular velocity) / time

In this case, the final angular velocity is 754.38 rad/s, the initial angular velocity is 0 rad/s (since the hard disk starts from rest), and the time is 3.7 seconds. Plugging in these values, we get:

I hope this helps and clarifies any confusion. Keep up the good work with your studies!

## 1. What is angular acceleration?

Angular acceleration refers to the rate of change of angular velocity over time. It is a measure of how quickly an object's rotational speed is changing.

## 2. How is angular acceleration calculated?

Angular acceleration is calculated by dividing the change in angular velocity by the change in time. The unit of angular acceleration is radians per second squared (rad/s2).

## 3. What is the average angular acceleration?

The average angular acceleration is the change in angular velocity divided by the total change in time. It is a measure of the overall change in rotational speed over a given period of time.

## 4. How is average angular acceleration different from instantaneous angular acceleration?

Instantaneous angular acceleration refers to the angular acceleration at a specific moment in time, whereas average angular acceleration considers the overall change in angular velocity over a period of time.

## 5. How is angular acceleration related to linear acceleration?

Angular acceleration and linear acceleration are related through the radius of rotation. The linear acceleration of an object moving along a circular path is equal to the angular acceleration multiplied by the radius of the circle.

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