Which has the smaller critical mass; U-235 that releases 2.5 neutrons per fission, or Pu-239 that releases 2.7 neutrons per fission?
A) U-235
B) Pu-239
C) both would have the same critical mass.
Answer: B
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A piston in an internal combustion engine applies torque during 
of each full rotation of the crankshaft to which it is connected. Suppose an 8-cylinder engine (8 such pistons) is running with its crankshaft turning at 2500rpm and produces 410J of work each second. What is the torque applied to the crank shaft by one of the engine’s eight pistons?
A. 3.8 Nm B. 1.6 Nm C. 0.47Nm D. 0.20 Nm
A circular window in the wall of a home has a diameter of 25 cm and is made of a single pane of glass 0.30 cm thick. Thermal conductivity for the glass is 0.63 W/mK. What heat is lost through the window in 12s if the temperature inside the house is
and outside is
A. 16 kJ B. 4.0 kJ C. 1.6 kJ D. 1.3 kJ E. 5.0 kJ
If energy is released when the parts of a system are allowed to disperse to infinity, its binding energy is
A. Positive. B. Negative. C. Zero. D. Not defined in such a case.
An electron moves horizontally across the Earth’s equator at a speed of 2.50 × 106 m/s and in a direction 35.08 N of E. At this point, the Earth’s magnetic field has a direction due north, is parallel to the surface, and has a value of 3.00 × 1025 T. What is the force acting on the electron due to its interaction with the Earth’s magnetic field?
1.6.88 × 10-18 N due west 2.6.88 × 10-18 N toward the Earth’s surface 3.9.83 × 10-18 N toward the Earth’s surface 4.9.83 × 10-18 N away from the Earth’s surface 5.4.00 × 10-18 N away from the Earth’s surface