A student slides her 80.0-kg desk across the level floor of her dormitory room a distance 2.00 m at constant speed. If the coefficient of kinetic friction between the desk and the floor is 0.400, how much work did she do?
A)
64.0 J
B)
1.57 kJ
C)
26.7 J
D)
628 J
E)
24.0 J
Question 2
In a nuclear power reactor of the type used to generate electricity, a neutron bombards a uranium nucleus, causing it to split into two large pieces (fission fragments) plus two or three neutrons.
Energy is released in this process in the form of electromagnetic radiation and kinetic energy. Which of the following is an accurate statement concerning what happens in such a fission process? A)
The electrical energy generated comes from the kinetic energy of the incident neutrons.
B)
The electrical energy generated comes from chemical energy stored in the electron bonds of the uranium atom.
C)
Electrical energy is generated because the fission fragments are electrically charged, whereas the uranium was electrically neutral.
D)
An intermediate step involves the fusion of protons to form helium nuclei, and energy is released in this process.
E)
The total mass of the particles after fission is less than the total mass of the particles (uranium nucleus plus one neutron) before fission, and this decrease in mass m is converted into energy E, where
E = mc2.
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Bill Viola. Room for St. John of the Cross. 1983.
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