How much energy is necessary to place three +2.0-µC point charges at the vertices of an equilateral triangle of side 2.0 cm if they started out extremely far away? (k = 1/4??0 = 9.0 × 109 N ? m2/C2)
A) 4.5 J
B) 5.4 J
C) 6.7 J
D) 7.6 J
B
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A uniform rod (mass = 2.0 kg, length = 0.60 m) is free to rotate about a frictionless pivot at one end. The rod is released from rest in the horizontal position. What is the magnitude of the angular acceleration of the rod at the instant it is 60° below the horizontal?
a. 15 rad/s2 b. 12 rad/s2 c. 18 rad/s2 d. 29 rad/s2 e. 23 rad/s2
Heat is a form of energy, and it has long been known that heat energy will naturally flow
A. from solids to liquids, but only when the solid is melting. B. from hot to cold objects. C. from cold to hot objects. D. from liquids to solids, except when the solid is melting.
Fusion reactions happen at a slower rate in bigger stars than in smaller ones.
a. true b. false
Copper atoms have a greater tendency to be reduced than iron atoms do. Was this good news or bad news for the Statue of Liberty, whose copper exterior was originally held together by steel rivets?
A) This was good news since the steel rivets prevented the copper from eroding. B) Electrons will preferentially flow from the iron to the copper and then onto oxygen. Corrosion is thus accelerated around the interface of these two metals. C) This combination of metals have no effect on each other and that is why engineers chose to use them together. D) This combination of metals caused the copper to oxidize and turn green.