Approximately how many other planetary systems have been discovered to date?
A) tens
B) hundreds
C) thousands
D) tens of thousands
E) millions
C
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Astronomers observe huge bubbles of hot gas, some over a thousand light-years across, in the Milky Way. What is their cause?
What will be an ideal response?
As you stand by the side of the road, a car approaches you at a constant speed, sounding its horn, and you hear a frequency of 76 Hz. After the car goes by, you hear a frequency of 65 Hz
What is the speed of the car? The speed of sound in the air is 343 m/s. A) 26 m/s B) 27 m/s C) 28 m/s D) 29 m/s E) 30 m/s
A stationary observer views the approach of a spaceship moving at a relativistic speed. The observer knows the ________ of the spaceship, as it moves past, is less than if it were stationary with respect to her.
A. height B. length C. density D. mass
A Geiger counter registers a count rate of 8,000 counts per minute from a sample of a radioisotope. The count rate 24 minutes later is 1,000 counts per minute. The half life of the radioisotope is
a. 3 minutes b. 4 minutes c. 6 minutes d. 8 minutes e. 12 minutes