Energy Conservation With Conservative Forces: A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case.
In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance?
A. Case A
B. Case B
C. Case C
D. Case D
E. The speed will be the same in all cases.
Answer: E
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The strength of low-carbon steel used in automobile bodies is achieved by ______________forming.
Fill in the blank(s) with the appropriate word(s).
The speed of sound depends on
A) its frequency. B) its amplitude. C) the medium in which it travels. D) all of the above E) none of the above
A mercury bath at 60°C is to be heated by immersing cylindrical electric heating rods, each 20 cm tall and 2 cm in diameter. Calculate the maximum electric power rating of a typical rod if its maximum surface temperature is 140°C.
GIVEN
• Cylindrical heating rods in a mercury bath
• Mercury temperature (T?) = 60°C
• Rod diameter (D) = 2 cm = 0.02 m
• Rod height (L) = 20 cm = 0.2 m
• Maximum surface temperature (Ts) = 140°C
FIND
• The maximum electric power rating ( q e) of a rod
ASSUMPTIONS
• Steady state
• The rods are in a vertical position
SKETCH
PROPERTIES AND CONSTANTS
for mercury at the mean temperature of 100°C
Thermal conductivity (k) = 10.51 W/(m K) Kinematic viscosity (?) = 0.093 × 10–6 m2/s Prandtl number (Pr) = 0.0162 Also Density at 50°C (?50) = 13,506 kg/m3
Density at 15°C (?150) = 13,264 kg/m3 To find the thermal expansion coefficient (?),
An pipe of length L that is open at both ends is resonating at its fundamental frequency. Which statement about the sound is correct?
A) The wavelength is 2L and there is a displacement node at the pipe's midpoint. B) The wavelength is 2L and there is a displacement antinode at the pipe's midpoint. C) The wavelength is L and there is a displacement node at the pipe's midpoint. D) The wavelength is L and there is a displacement antinode at the pipe's midpoint.