Suppose you electrically charge a comb by running it through your hair. If you then shake this comb back and forth one time every second, you will create
A) an electromagnetic wave having a frequency of 1 Hz and a speed of 300,000 km/s.
B) a sound wave having a frequency of 1 Hz and a speed of 300,000 km/s.
C) an electromagnetic field that vibrates at a frequency of 1 Hz, but no electromagnetic wave is created.
D) the tooth fairy.
E) a sound wave having a wavelength of 300,000 km and a speed of 300,000 km/s.
A
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A long thin rod of length L has a linear density ?(x) = Ax where x is the distance from the left end of the rod
(a) How far is the center of mass of the rod from the left end of the rod? (b) What is the mass of the rod?
A charged comb attracts bits of neutral dust in the air. This happens because
A. the dust becomes polarized. B. the dust is a good conductor. C. the dust becomes charged by induction. D. the dust grounds the comb.
When introduced into a region where an electric field is present, a proton with initial velocity 
will eventually move
A. along an electric field line, in the positive direction of the line. B. along an electric field line, in the negative direction of the line. C. to a point of decreased potential. D. to a point of decreased potential. E. as described in both (a) and (c).
A proton falls through a potential drop of 400 V. How much is the change of potential energy of this proton in falling through this potential drop?
A) 6.4 × 10-16 J B) -6.4 × 10-16 J C) 17 × 10-16 J D) -4000 J E) 4000 J