Lab 11

#$&*

course Phy 201

Balancing Dominos on a Foam Beam

A foam beam with three dominoes was balanced using a fourth domino as its fulcrum.

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

****

Unbalanced

from center to domno on single side is = 18cm

from center to first domino on opposite side is 2.7 cm and 10 cm

Positive direction is right

15000 dynes acting from each domino

Torque is positive

Tnet= F1 270,000 dynes *cm

F2 -40,500 dynes *cm

F3 -150,000 dynes *cm

SUM of Tau = +90,000 dynes *cm (NOT at equilibrium)

I= SUM mr^2

r= 15.35 cm

m=45000 dynes

I= 4.77 *E11 dynes*cm^2

@&
You need to calculate m r^2 for each domino separately. They are all at different distances from the fulcrum, so they all have different values of r. This makes a significant difference in the result for the moment of inertia.
*@

@&
I suspect you squared the entire m * r expression, instead of squaring r then multiplying by m. The moment of inertia wil be on the order of 10^6 or 10^7 dynes * cm^2, not 10^11.

*@

Angular Acceleration

alpha = 90000 dynes*cm/ 4.77 E11 dynes*cm^2

alpha = 1.88 E-7 rad/sec^2

@&
Good, but your moment of inertia value will change (see above).
*@

Balanced System

Domino on left to center = 18cm

2 dominoes on the right are 3.5cm and 13.5 cm from center

Tnet= 17cm * 15000 dynes= 255,000 dynes*cm

-3.5cm * 15000 dynes = -52,500 dyens *cm

-13.5cm * 15000 dynes = -202,500

Tnet= 0cm/dynes (at equilibrium

#$&*

For the balanced system:

· Report the torque about the balancing point of each domino or domino stack.

· Report the net torque of the system about the balancing point.

****

ALL ABOVE

#$&*

For the unbalanced system:

· Report the torque about the balancing point of each domino or domino stack.

· Report the net torque of the system about the balancing point.

· Report the moment of inertia of the system.

****

ALL ABOVE

#$&*

What should therefore be the angular acceleration of the system?

****

ALL ABOVE

#$&*

@&
Good, but you need to correct your moment of inertia calculation and your angular acceleration. You're on the right track with that, so it shouldn't take you more than a few minutes.

&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
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Lab 11

@& You need to calculate m r^2 for each domino separately. They are all at different distances from the fulcrum, so they all have different values of r. This makes a significant difference in the result for the moment of inertia. *@

@& I suspect you squared the entire m * r expression, instead of squaring r then multiplying by m. The moment of inertia wil be on the order of 10^6 or 10^7 dynes * cm^2, not 10^11. *@

@& Good, but your moment of inertia value will change (see above). *@

@& Good, but you need to correct your moment of inertia calculation and your angular acceleration. You're on the right track with that, so it shouldn't take you more than a few minutes.

@&
You need to calculate m r^2 for each domino separately. They are all at different distances from the fulcrum, so they all have different values of r. This makes a significant difference in the result for the moment of inertia.
*@

@&
I suspect you squared the entire m * r expression, instead of squaring r then multiplying by m. The moment of inertia wil be on the order of 10^6 or 10^7 dynes * cm^2, not 10^11.

*@

@&
Good, but your moment of inertia value will change (see above).
*@

@&
Good, but you need to correct your moment of inertia calculation and your angular acceleration. You're on the right track with that, so it shouldn't take you more than a few minutes.