#$&*
Phy 121
Your 'cq_1_20.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** CQ_1_20.1_labelMessages **
Copy the problem below into a text editor or word processor.
• This form accepts only text so a text editor such as Notepad is fine.
• You might prefer for your own reasons to use a word processor (for example the formatting features might help you organize your answer and explanations), but note that formatting will be lost when you submit your work through the form.
• If you use a word processor avoid using special characters or symbols, which would require more of your time to create and will not be represented correctly by the form.
• As you will see within the first few assignments, there is an easily-learned keyboard-based shorthand that doesn't look quite as pretty as word-processor symbols, but which gets the job done much more efficiently.
You should enter your answers using the text editor or word processor. You will then copy-and-paste it into the box below, and submit.
________________________________________
The situation here is similar to that depicted above, though the distances of the rubber bands from the center are different. The die on which the strap rotates is not visible, but is attached to the tabletop; the blue push pin constrains the system to rotate about a vertical axis through the center of the die.
The problem:
The metal strap used in the Angular Velocity of a Strap experiment is constrained by a vertical push pin to rotate about a hole in a die. The die is glued in place to a massive tabletop. A rubber band is attached to a point 15 cm from the axis and stretched so that it exerts a force of 3 Newtons, directed perpendicular to the rod. If this force is unopposed it will accelerate the system rapidly. You want to attach a second rubber band 5 cm from the axis to prevent the system from rotating.
• How much force will that rubber band have to exert?
answer/question/discussion: ->->->->->->->->->->->-> :
This rubber band will have to exert 9 Newtons of force because 15*3=45 and 45/5=9.
#$&*
• Once both of these forces are in place and the system is stationary, what (if anything) will happen if the glue holding the die to the tabletop comes loose?
answer/question/discussion: ->->->->->->->->->->->-> :
Nothing will happen because the strap has reached equilibrium.
@&
A 9 Newton force and a 3 Newton force cannot be in equilibrium.
The two are in rotational equilibrium, but not translational equilibrium.
The strap will accelerate initially in response to the net force of 6 Newtons. The strap will no longer be constrained to rotate about its previous axis, and the unbalanced forces will rotate it about a new axis.
Full analysis of this motion is beyond the scope of the course. The bottom line is that in the absence of the stabilizing force exerted by the die and pin, the strap will change its position, its position, velocity, angular position and angular velocity will all change.
*@
#$&*
** **
15 minutes
** **
&#Good responses. See my notes and let me know if you have questions. &#