Nexrad radar uses a frequency of 2.7 GHz to measure the speed of cloud systems. The radio waves from the transmitter are sent outward to the cloud system and reflected back, Doppler shifted. A Nexrad system observes clouds moving toward the transmitter at 21 m/s. What is the difference between the transmitted frequency and the frequency received after reflection off the cloud surface?
A. 380 Hz
B. 760 Hz
C. 570 Hz
D. 190 Hz
A. 380 Hz
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When I was a teenager, I saw a Candid Camera sequence in which they filmed a person struggling with a suitcase that (unknown to that person) contained a large and rapidly spinning gyroscope. Imagine you are carrying such a suitcase where the gyroscope’s angular velocity is oriented horizontally to your right as you carry it in your right hand. Imagine you try to make a left turn, thus turning the suitcase to the left around a vertical axis. What does the suitcase do?
A. It turns to the left as one would expect. B. It tries to turn instead to the right. C. It tries to rotate around a horizontal axis, with its right face turning upward. D. It tries to rotate around a horizontal axis, with its left face turning upward. E. It tries to rotate around a rightward axis, with its front edge moving up.
Two people stand on different floors of an outdoor stairway. One is 6 m above the ground and the other is 12 m above the ground. The person on the lower floor throws a ball upward with a speed of 15 m/s and the other person just drops hers. Ignoring air resistance, which ball hits the ground at a higher speed?
A. The one thrown upward B. They both hit the ground with the same speed C. The one that is dropped
An 84-kW AM radio station broadcasts at 1000 kHz . How many photons are emitted each second by the transmitting antenna? (h = 6.626 × 10-34 J • s)
A) 1.3 × 1032 B) 2.9 × 1024 C) 6.3 × 1012 D) 1.4 × 1015
Ultraviolet radiation from a star:
A) gets almost completely absorbed before it reaches Earth's surface. B) has a wavelength that is longer than the visible light emitted by the star. C) has a wavelength that is shorter than the X-rays emitted by the star. D) reaches most of Earth's surface through atmospheric windows.