A camera is used to photograph the full moon, which has an angular diameter of 0.51°. The image on the film is 2.5 mm in diameter. What is the focal length of the lens?
a. 6.3 mm
c. 13 mm
b. 280 mm
d. 450 mm
B
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If a dense 20.0-kg object is falling in air at half its terminal velocity, what is the drag force on the object at this moment?
A. 24.5 N B. 49.0 N C. 69.3 N D. 98.0 N E. 139 N
Three particles are placed in the xy plane. A 30-g particle is located at (3, 4) m, and a 40-g particle is located at (-2, -2) m. Where must a 20-g particle be placed so that the center of mass of the three-particle system is at the origin?
a. (-3, -1) m b. (+1, +3) m c. (+3, -1) m d. (-1, -3) m e. (-0.5, -2) m
A 3.0 cm tall statue is 24. cm in front of a concave mirror. The mirror radius of curvature is 20. cm. (a) Is the image real or virtual? (b) How far is the image from the mirror? (c) Is the image upright or inverted? (d) How high is the image?
What will be an ideal response?
If an object feels cold to the touch, the only statement that you can make that must be correct is that
a. the object has a smaller coefficient of thermal conductivity than your hand. b. the volume of the object will increase while it is in contact with your hand. c. the object contains less thermal energy than your hand. d. the object is at a lower temperature than your hand. e. the object cannot be a liquid.