Prior to the 1990s, most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks. How do we now know that this hypothesis was wrong?
A) We now know that gamma-ray bursts come not from neutron stars but from black holes.
B) Theoretical work has proven that gamma rays cannot be produced in accretion disks.
C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky.
D) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts occur too frequently to be attributed to neutron stars.
E) Observations from the Compton Gamma-Ray Observatory have allowed us to trace gamma-ray bursts to pulsating variable stars in distant galaxies.
C
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An aluminum kettle (mass = 100 g) of pure water (mass = 60 g) is at room temperature (20°C). The kettle and its contents are placed on a 1000-Watt electric burner and heated to boiling
Assuming that all the heat from the burner heats the kettle and its contents and that a negligible amount of water evaporates before boiling begins, calculate the amount of time required to bring the water to a boil. A) 3.5 min B) 8.1 min C) 4.9 min D) 7.3 min E) 4.0 min
A new electric power plant has an efficiency of 42%. For every 100 barrels of oil needed to run the turbine, how many are essentially lost as waste heat (in barrels of oil) to the environment?
a. 21 b. 42 c. 58 d. 10 e. 79
What kind of gas is most affected by thermal escape?
A. greenhouse gases B. light gases C. all gases equally
A box is sliding down an incline tilted at a 12.0° angle above horizontal
The box is initially sliding down the incline at a speed of 1.50 m/s. The coefficient of kinetic friction between the box and the incline is 0.340. How far does the box slide down the incline before coming to rest? A) 0.920 m B) 2.33 m C) 1.78 m D) 0.720 m E) The box does not stop. It accelerates down the plane.