A car approaches a stationary police car at 36 m/s. The frequency of the siren (relative to the police car) is 500 Hz. What is the frequency (in Hz) heard by an observer in the moving car as he approaches the police car? (Assume the velocity of sound in air is 343 m/s.)
a. 220
b. 448
c. 526
d. 552
e. 383
D
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The Chandrasekhar limit defines the ____
a. maximum mass of a white dwarf b. lifetime of a white dwarf c. temperature for carbon fusion d. separation between medium- and high-mass stellar evolution e. stellar surface temperature needed to ionize a planetary nebula
An air-filled parallel-plate capacitor is connected to a battery and allowed to charge up. Now a slab of dielectric material is placed between the plates of the capacitor while the capacitor is still connected to the battery
After this is done, we find that A) the energy stored in the capacitor had decreased. B) the voltage across the capacitor had increased. C) the charge on the capacitor had increased. D) the charge on the capacitor had not changed. E) None of these choices is true.
If the net force acting on an object is in the positive x-direction, the object moves only in the positive x-direction
1.True 2.False
Which of the following is NOT a property of elliptical galaxies?
A. They have little dust or cold gas. B. They have prominent spiral arms. C. They contain mostly old (Pop II) stars. D. Stars are distributed smoothly throughout their volume.