A object is 20 cm in front of a concave mirror, and the image is 5.0 cm in front of the mirror. What is the focal length of the mirror?
A) 0.25 cm
B) 25 cm
C) 6.7 cm
D) 4.0 cm
E) 2.1 cm
D
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A sound level of 80 dB has twenty times the amplitude of a 60 dB sound
a. True b. False Indicate whether the statement is true or false
The efficiency of inexpensive solar cells is closest to
A. 1% B.12% c. 65% D. 100%
Carbon dioxide and water molecules in the atmosphere will absorb:
a. infrared light. c. ultraviolet light. b. visible light. d. radio waves.
A person ties a rock to a string and whirls it around in a vertical circle such that sometimes the rock is going straight upward and sometimes the rock is going straight down
She whirls the rock at the minimum speed (constant in time) such that the string is always taut (no sag). If she were to use a longer string, she would have to whirl the rock at a A) higher velocity. B) lower velocity. C) the same velocity.