Force on a Wire: A thin copper rod 1.0 m long has a mass of 0.050 kg and is in a magnetic field of 0.10 T. What minimum current in the rod is needed in order for the magnetic force to balance the weight of the rod?
A. 1.2 A
B. 2.5 A
C. 4.9 A
D. 9.8 A
Answer: C
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A merry-go-round is set into motion with a child on board. The rotational speed of the merry-go-round ________ as the child moves inward along a radius.
Fill in the blank(s) with the appropriate word(s).
Complete the following induced reaction 
+?
A. 
B. 
C. 
D. 
What problem is adaptive optics designed to correct?
A) the opacity of the Earth's atmosphere B) defects in the optical figuring, such as with the adaptive optics on HST C) slight tracking errors in trying to compensate for our unsteady rotation D) the effects of atmospheric turbulence E) the absorption of ultraviolet by the ozone layer
Magnifying Glass With the Image at Infinity: A lens of focal length 90 mm is used as a magnifier by a person with a near point of 25 cm. The object being viewed is 9.9 mm long, and is positioned at the focal point of the lens. What is the angle subtended by the image at infinity, in milliradians?
A. 110 mrad B. 73 mrad C. 37 mrad D. 147 mrad E. 183 mrad