Lab 2

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course Phy 201

Strap coasting to rest

You observed time and angular displacement for three trials of a strap coasting to rest.

Insert a copy of your data here, along with any previously submitted work you wish to include:

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Avg Angular Velocity for each

6 seconds= 720degrees (12.56 rad)

12 seconds= 1200degrees (20.9 rad)

3 seconds= 600 degrees (10.5 rad)

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For each trial:

What was the average angular velocity? Express is terms of degrees and seconds, as well as revolutions and seconds.

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1. 2.11 rad/sec or .3 rev/sec

2. 1.77 r/s or .28 rev/sec

3. 3.5 r/s or .56 rev/sec

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Assuming uniform angular acceleration, what was the angular acceleration of the system? Express is terms of degrees and seconds, as well as revolutions and seconds.

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aplha= d'theta/d't

1. -.35 rad/s^2 or -.05 revolutions/s^2

2. -.14 rad/s^2 or -.14 rev/s^2

3. -1.1 rad/s^2 or -.19 rev/s^2

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Was there a trend in the angular acceleration vs. average angular velocity?

****

Yes bc angular acceleration and average angular velocity are related due the R.O.C definition.

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@&
That's an important relationship but not a trend.

For example, if the angular acceleration increased or decreased along with angular velocity, that would be a trend.

There doesn't appear to be such a trend in your results.
*@

The strap has a mass of about 70 grams and a length of about 30 cm. What average torque was required to bring it to rest in each trial?

****

Tnet= Iomega

I=SUM mr^2

which I is equal to 230.8 kg*m^2

@&
The moment of inertia is very much smaller than that. You have the right units, so I suspect you're basically doing this right, but without a little explanation I can't tell what you put together to get your result.
*@

Trial 1

Tnet= 230.8 kg*m^2 *(-.35rad/s^2)

Tnet= 80.78 kg*m^2*rad/s^2

Trial 2

Tnet= 32.3 kg m^2 rad/s^2

Trial 3

Tnet= 254 kg m^2 rad/s^2

@&
Good, but that moment of inertia isn't right, and that throws off your torque calculations.

This should be really easy to correct, but I need to know the details of your calculation. Can you clarify how you calculated the moment of inertia?
*@

Lab 2

@& That's an important relationship but not a trend. For example, if the angular acceleration increased or decreased along with angular velocity, that would be a trend. There doesn't appear to be such a trend in your results. *@

@& The moment of inertia is very much smaller than that. You have the right units, so I suspect you're basically doing this right, but without a little explanation I can't tell what you put together to get your result. *@

@& Good, but that moment of inertia isn't right, and that throws off your torque calculations. This should be really easy to correct, but I need to know the details of your calculation. Can you clarify how you calculated the moment of inertia? *@

@&
That's an important relationship but not a trend.

For example, if the angular acceleration increased or decreased along with angular velocity, that would be a trend.

There doesn't appear to be such a trend in your results.
*@

@&
The moment of inertia is very much smaller than that. You have the right units, so I suspect you're basically doing this right, but without a little explanation I can't tell what you put together to get your result.
*@

@&
Good, but that moment of inertia isn't right, and that throws off your torque calculations.

This should be really easy to correct, but I need to know the details of your calculation. Can you clarify how you calculated the moment of inertia?
*@