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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During the time before fusion begins, a protostar's core gradually
A) shrinks and heats. B) shrinks and cools. C) shrinks and maintains a constant temperature. D) expands and cools.
In a contest, two tractors pull two identical blocks of stone the same distance over identical surfaces. However, block A is moving twice as fast as block B when it crosses the finish line. Which statement is correct?
A. Block A has twice as much kinetic energy as block B. B. Block B has lost twice as much kinetic energy to friction as block A. C. Block B has lost twice as much kinetic energy as block A. D. Both blocks have had equal losses of energy to friction. E. No energy is lost to friction because the ground has no displacement.
The unit of electric current is the ______________
Fill in the blank(s) with correct word
Two bulbs are shown in a circuit that surrounds a region of increasing magnetic field directed out of the page. When the switch is closed,
a.
bulb 1 glows more brightly.
b.
bulb 2 glows more brightly.
c.
both bulbs continue to glow with the same brightness.
d.
bulb 1 goes out.
e.
bulb 2 goes out.