Briefly explain how a fiber made of oriented ultra-high-molecular-weight polyethylene can be much stronger than structural steel in tension, but perpendicular to the fiber axis, its hardness is much less than that of steel.
What will be an ideal response?
In tension the force is pulling on the strong covalent carbon-carbon bonds in the long chain molecules oriented along the fiber axis. In a hardness test perpendicular to the fiber axis the indenter displaces the weak van der Waals bonds that hold different fibers together.
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One member of a pair of parallel conducting plates has potential 17 V. An electron is ejected from that plate at potential and travels the other plate, attaining a velocity of 
when it arrives. What is the potential of the second plate? The mass of the electron is 
kg.
A. 157 V B. 89 V C. 72 V D. -54 V E. 142 V
A cannonball has more kinetic energy than the recoiling cannon from which it is fired because the force on the ball
A) is more concentrated. B) meets less resistance than the cannon on the ground. C) acts over a longer distance.
In an isovolumetric process
a. the temperature remains constant. b. no heat is transferred between a system and its surroundings. c. the pressure remains constant. d. the volume remains constant. e. the internal energy is constant.
What is the typical main sequence lifetime of an M-type star?
A) one million years B) ten million years C) one billion years D) ten billion years E) a trillion years