Consider a student whose mass is 70 kg. If all his mass were converted to electrical energy, for how many years could he keep a 100-W light bulb burning? (c = 3.0 × 108 m/s)
What will be an ideal response?
6.3 × 1016 s = 2.0 billion years!
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An aluminum bar of diameter d 5 52 mm is twisted by torques T1 at the ends. The allowable shear stress is 65 MPa. The maximum permis-sible torque T1 is approximately:
(A) 1450 N?m
(B) 1675 N?m
(C) 1710 N?m
(D) 1800 N?m
Two infinite, uniformly charged, flat surfaces are mutually perpendicular. One of the sheets has a charge density of +60 pC/m2, and the other carries a charge density of ?80 pC/m2. What is the magnitude of the electric field at any point not on either surface?
A. 1.1 N/C B. 5.6 N/C C. 7.9 N/C D. 3.8 N/C E. 4.0 N/C
In the Southern Hemisphere, the direction of Ekman transport is
A) at a 45° angle from the wind direction. B) parallel to the wind direction. C) to the right of the wind direction. D) to the left of the wind direction.
An electron moving in the positive x direction experiences a magnetic force in the positive z direction. If Bx = 0, what is the direction of the magnetic field?
a. negative y direction b. positive y direction c. negative z direction d. positive z direction e. negative x direction