Statics PREFLIGHT

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The following questions refer to the material you were to read in preparation for the lesson.

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Young's Modulus

An aluminum bar (Young's modulus of  7.0 x 109 N/m2) is stretched by a  force as shown in the animation (position is in centimeters and time is in seconds). Assume the bar has a square cross section. What is the force required to elongate the aluminum? Start
1.5 x 104 N
1.5 x 108 N
3.1 x 105 N
1.5 x 105 N
Other (please explain below)




honors extra

Don't try this at home

This puzzle is provided by Dr. David Smith, a physics professor at the University of the Virgin Islands and an accomplished stilt walker.

The pictures below show Dave and Demoise in static equilibrium before and after Dave extends his arms. The point of contact between the stilts and floor did not change as Dave extended his arms.

Consider the following three cases:
Static case with arms not extended (first picture.)
Theoretically, could this position be maintained on a frictionless surface?


Static case with arms extended (second picture.)
Theoretically, could this position be maintained on a frictionless surface?


Transition between the static positions, Dave extends his arms and moves Demoise outward.
Theoretically, could this move be accomplished on a frictionless surface?



Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):



You may change your mind as often as you wish. When you are satisfied with your responses, click the SUBMIT button.

I received no help from anyone on this assignment.