A 12-kg projectile is launched with an initial vertical speed of 20 m/s. It rises to a maximum height of 18 m above the launch point. What is the change in mechanical energy caused by the dissipative (air) resistive force on the projectile during this ascent?
A. ?0.64 kJ
B. ?0.40 kJ
C. ?0.52 kJ
D. ?0.28 kJ
E. ?0.76 kJ
Answer: D
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A cube of water ice (? = 0.917 × 103 kg/m3) is placed in mercury (? = 13.6 × 103 kg/m3), which is liquid at 0° Celsius. If we ignore any possible melting of the ice cube and problems with the surface tension of mercury, the fraction of the ice cube that floats above the surface of the mercury is
A. 0.067 4. B. 0.073 5. C. 0.926. D. 0.933. E. 1.00.
Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
a. Y has a negative charge. b. Z has a negative charge. c. Y has a positive charge. d. Z has a positive charge. e. Z is neutral (has no net charge.)
Equipotential surfaces around a point charge are
a. spherical. c. planar. b. cylindrical. d. none of these choices.
A square loop (length along one side = 20 cm) rotates in a constant magnetic field which has a magnitude of 2.0 T. At an instant when the angle between the field and the normal to the plane of the loop is equal to 20° and increasing at the rate of 10°/s, what is the magnitude of the induced emf in the loop?
A. 13 mV B. 0.27 V C. 4.8 mV D. 14 mV E. 2.2 mV