Thursday, November 8, 2012

Ch 6 Momentum Collisions Conceptual Questions Solutions Even-Numbered

(2)  If two objects collide and one is initially at rest, (a) is it possible for both to be at rest after the collision? (b) Is it possible for only one to be at rest after the collision? Explain.


(4)  America will never forget the terrorist attack on Sept 11th, 2001. One commentator remarked that the force of the explosion at the Twin Towers was strong enough to blow glass and parts of the steel structure to small fragments. Yet the television coverage showed thousands of sheets of paper floating down, many still intact. Explain how that could be.


  The glass, concrete, and steel were part of a rigid structure that shattered upon impact of the airplanes with the towers
and upon collapse of the buildings as the steel support structures weakened due to high temperatures of the
burning fuel. The sheets of paper floating down were probably not in the vicinity of the direct impact, where they
would have burned after being exposed to very high temperatures. The papers were most likely situated on desktops
or open file cabinets and were blown out of the buildings as they collapsed.



(8)  (a)  If two automobiles collide, they usually do not stick together.  Does this mean the collision is elastic?  (b)  Explain why a head-on collision is likely to be more dangerous than other types of collisions.


(10)  A large bedsheet is held vertically by two students. A third student, who happens to be the star pitcher on the baseball team, throws a raw egg at the sheet. Explain why the egg doesn't break when it hits the sheet, regardless of its initial speed.  


(14)  An open box slides across a frictionless, icy surface of a frozen lake.  What happens to the speed of the box as water from a rain shower falls vertically downward into the box? Explain.


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