A ball falls to the ground from height h and bounces to height h'. Momentum is conserved in the ball-earth system
a. no matter what height h' it reaches.
b. only if h' < h.
c. only if h' = h.
d. only if h' > h.
e. only if h' ? h.
a
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At atmospheric pressure, 45 moles of liquid helium are vaporized at its boiling point of 4.22 K. The heat of vaporization of helium, at atmospheric pressure, is 2.09 × 104 J/kg,
and the atomic weight of helium is 4.00 g/mol. The change in the entropy of the helium, as it vaporizes, is closest to A) 890 J/K. B) 14,000 J/K. C) 18,000 J/K. D) -9400 J/K. E) -14,000 J/K.
A 1 500-kg car rounds an unbanked curve with a radius of 52 m at a speed of 12.0 m/s. What minimum coefficient of friction must exist between the road and tires to prevent the car from slipping? (g = 9.8 m/s2)
a. 0.024 b. 0.23 c. 0.28 d. 1.2
Many specialized applications (ranging from advanced gas-turbine blades to medical devices and implants) require metal components that are coated with protective material layer. In a manufacturing plant for such coatings, infrared lamp is used for curing the coating on metal plates. The lamp provides uniform irradiation of which a flux of 1600 W/m2 is absorbed by the metal plate surface, which has an emissivity of 0.5 for the radiation at the temperature of the coating. Air is used to cool the plate, which is kept in an enclosed environment, and it enters the enclosure at 200C and leaves from the coating process at 300C. (a) If the convective heat transfer coefficient between the coated plate surface and cooling air is 15 W/ (m2 K), estimate the temperature of coating on plate surface.
(b) If the engineer who invented believes that the cure temperature (or surface temperature) of 500C provides a coating with better durability, estimate the infrared lamp irradiation necessary to attain the required average cure temperature for the process.
GIVEN
FIND
- Temperature of coating on plate surface
- Infrared lamp irradiation necessary to attain required cure temperature.
ASSUMPTIONS
- Steady state conditions prevail
- Other heat loss to surrounding is negligible
Suppose a nucleus has 50 protons and 50 neutrons. This places the nucleus to the right of the line of stability; therefore, it will most likely undergo radioactive decay. Given its place on the plot, what are the most likely types of radioactive decay?
a. Alpha decay. b. Beta plus decay and electron capture. c. All of the above. d. Gamma emission. e. None of the above, because the nucleus is stable.