Bats can detect small objects such as insects that are of a size on the order of a wavelength. If bats emit a chirp at a frequency of 60 kHz and the speed of soundwaves in air is 330 m/s, what is the smallest size insect they can detect?
a. 1.5 mm
b. 3.5 mm
c. 5.5 mm
d. 7.5 mm
e. 9.8 mm
c
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A hockey puck slides across a frozen pond. If ice friction and air resistance are neglected, the force needed to keep the puck sliding at constant velocity is
A) 0 N. B) equal to the weight of the puck. C) the weight of the puck divided by the mass of the puck. D) the mass of the puck multiplied by 10 m/s2. E) none of the above
A certain kind of lightbulb carries 0.5 amperes of current when connected to a 120 volt AC circuit. What is its power rating?
A. 75 W B. 240 W C. 100 W D. 60 W
Doubling the diameter of a loop of wire produces what change of induced emf?
A. The induced emf is 4 times as much. B. The induced emf is twice as much. C. There is no change in the induced emf. D. The induced emf is 6.28 times as much.
Thermal Expansion: The coefficient of linear expansion of aluminum is 24.0 × 10-6 K-1, and the density of aluminum at 0°C is 2.70 × 103 kg/m3. What is the density of aluminum at 300°C?
A. 3.93 × 103 kg/m3 B. 2.73 × 103 kg/m3 C. 2.70 × 103 kg/m3 D. 2.67 × 103 kg/m3 E. 2.64 × 103 kg/m3