How much power does a sphere with a radius of 10 cm radiate into empty space if is has an emissivity of 1.0 and is kept at a temperature of 400 K? (? = 5.67 × 10-8 W/m2 ? K4 )
A) 60 W
B) 70 W
C) 180 W
D) 210 W
E) 360 W
C
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Hydrostatic equilibrium refers to the balance between weight and pressure
a. True b. False Indicate whether the statement is true or false
A 60-kg person rides down an icy hill of 20° slope while standing on a 3.0-kg flat-bottomed bathroom scale. Assume there is no frictional force between the bottom of the scale and the hill. The static friction force the scale exerts on the person is
A. 0 N. B. 201 N. C. 211 N. D. 553 N. E. 580 N.
When a current of 2.0 A flows in the 100-turn primary of an ideal transformer, this causes 14 A to flow in the secondary. How many turns are in the secondary?
A) 14 B) 4 C) 114 D) 356 E) 700
This photo shows the diffraction pattern in the shadow of a penny. If light bends around the edges of a penny to produce a bright spot exactly at the center, why are there no bright spots in places other than the center?
a. There are additional spots, but the one in the center is brightest. b. The penny acts like a lens and the bright spot is simply a tiny image of the penny. c. The center is equidistant from all parts of the penny's edge, therefore waves arrive "in step" at the center to add and produce a bright spot, but arrive out of step and cancel elsewhere. d. Superposition and interference of waves from the light occurs only at the center. e. The bright spot is merely an optical illusion.