Astronomers can detect the spin rates of stars by
A) their temperature.
B) changes in temperature.
C) absorption spectra.
D) the Doppler effect.
E) all of the above
Answer: D
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Power: In the circuit shown in the figure, the 60-Hz ac source has a voltage amplitude of 120 V, the capacitive reactance is 850 ?, and the inductive reactance is 340 ?. What is the resistance R if the power factor is 0.80?
A. 680 ? B. 610 ? C. 540 ? D. 460 ? E. 380 ?
A projectile is projected from the origin with a velocity of 30.0 m/s at an angle of 40.0 degrees above the horizontal. What is the position vector when the projectile is at the maximum height?
A. X = 45.2 m, Y = 19.0 m B. X = 21.1 m, Y = 19.0 m C. X = 51.1 m, Y = 21.1 m D. X = 45.2 m, Y = 21.1 m E. X = 19.0 m, Y = 17.5 m
The momentum of a photon is inversely proportional to its total energy
Indicate whether the statement is true or false
The mass of visible matter in a galaxy can be estimated by measuring its luminosity. When this is compared with the measured mass of the galaxy, astronomers find that ____
a. the measured mass is about ten times the estimated mass, due to the effects of the central black hole b. the measured mass is approximately equal to the estimated mass c. there is no clear relationship between the estimated and measured mass d. the measured mass is about ten times the estimated mass, due to the effects of dark matter e. the estimated mass is about ten times the measured mass, due to the effects of dark matter