The heat of fusion of lead is 5.9 kcal/kg, the heat of vaporization is 207. cal/kg, and its melting point is 328°C. How much heat is required to melt 50. g of lead initially at 23°C? (The specific heat of lead is 0.031 kcal/kg-C°.)
What will be an ideal response?
0.77 kcal
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A force of 10.0 N is applied to a wire with an un-stretched length of 4.00 m and a diameter of 5.00 mm. If the wire changed length by 1.20 mm, then the stress in the wire is
a. 
b. 
c. 
d. 
e. 
The first postulate of special relativity says that:
a. the laws of physics are all the same. b. the laws of physics are the same in all reference systems. c. the laws of physics are the same in all non-inertial reference systems. d. the laws of physics are the same in all inertial reference systems. e. the laws of physics are the same in all closed reference systems.
When an object is polarized, it
A. must contain more positive charge than negative charge. B. must contain more negative charge than positive charge. C. will have a separation of positive and negative charge. D. must be illuminated by polarized light. E. must be made of metal.
What eventually halts the gravitational collapse of an interstellar gas cloud that forms an object that is not massive enough to become a star?
A) Nothing; all collapsing gas clouds become black holes. B) the crowding of electrons in the core C) A critical fraction of the gas has been driven further into space. D) the central object becoming hot enough to sustain nuclear fusion in its core