How have astronomers interpreted the unexpectedly fast rotation of galaxies?
A.) Scientific measurements must be wrong.
B.) Galaxies may be breaking up.
C.) There must be a lot of dark matter whose gravity can be felt but not seen.
D.) These galaxies must have had collisions.
E.) B, C, and D.
Ans: C.) There must be a lot of dark matter whose gravity can be felt but not seen.
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Photoelectric Effect: A beam of light falling on a metal surface is causing electrons to be ejected from the surface. If we now double the frequency of the light, which of the following statements are correct? (There could be more than one correct choice.)
A. The kinetic energy of the ejected electrons doubles. B. The speed of the ejected electrons doubles. C. The number of electrons ejected per second doubles. D. Twice as many photons hit the metal surface as before. E. None of these things occur.
Suppose that the build-up of fatty tissue on the wall of an artery decreased the radius by 10%. By how much would the pressure provided by the heart have to be increased to maintain a constant blood flow?
What will be an ideal response?
An AC generator consists of 6 turns of wire. Each turn has an area of 0.040 m2. The loop rotates in a uniform field (B = 0.20 T) at a constant frequency of 50 Hz. What is the maximum induced emf?
A. 13 V B. 2.4 V C. 3.0 V D. 15 V E. 4.8 V
A 0.120-pF parallel-plate capacitor is charged to a potential difference of 10.0 V and then disconnected from the battery. A cosmic ray burst creates 1.00 × 10^6 electrons and 1.00 × 10^6 positive charges between the plates. If the charges do not recombine, but reach the oppositely charged plates, by how much is the potential difference between the capacitor plates reduced?
a. 1.33 V b. 7.34 V c. 8.67 V d. 1,330 V e. 8,670 V