A piece of taffy slams into and sticks to an identical piece of taffy at rest. The momentum of the combined pieces after the collision is the same as before the collision, but this is not true of the kinetic energy, which partly degrades into heat
What percentage of the kinetic energy becomes heat?
A) 0%
B) 25%
C) 50%
D) 75%
E) need more information
Answer: C
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A particle with a positive charge sits at rest near the south pole of a magnet as shown below. What is the direction of the magnetic force on the particle? Choose from the answers provided to the right and below the diagram.
A.A
B.B
C.C
D.D
E. Toward the viewer
F. Away from the viewer
T. There is no magnetic force on the particle.
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
A) The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form. B) The temperature of the universe can be found by taking an average over the entire sky, but individual stars will create peaks in the spectrum over small angles. C) Dark matter consisting of WIMPs greatly smooths out the spectrum, but the small patches of "light" matter create peaks in the spectrum. D) The overall structure of the universe is very uniform, but the synthesis of different elements produces varying signatures within the background spectrum. E) The overall structure of the universe is very uniform, but intervening gas between us and the era of nuclei absorbs wavelengths depending on the composition and redshift of the gas.
A heat engine has an efficiency of 31.4% and receives 8.72 kJ of heat per cycle
(a) How much work does it perform in each cycle? (b) How much heat does it exhaust in each cycle? What will be an ideal response?
A vibrating guitar string emits a tone simultaneously with one from a 500-Hz tuning fork. If a beat frequency of 4 Hz results, what is the frequency of vibration of the string?
a. 2500 Hz c. 504 Hz b. 496 Hz d. Either choice B or C is valid.