A point on the string of a violin moves up and down in simple harmonic motion with an amplitude of 1.24 mm and a frequency of 875 Hz
(a) What is the maximum speed of that point in SI units? (b) What is the maximum acceleration of the point in SI units?
(a) 6.82 m/s (b) 3.75 × 104 m/s2
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Addition by 1. Components: Vector 
has a magnitude of 6.0 m and points 30° south of east. Vector 
has a magnitude of 4.0 m and points 30° west of south. The resultant vector 
+ 
is given by
A. 7.2 m at an angle of 64° south of east. B. 3.3 m at an angle of 64° south of east. C. 9.8 m at an angle of 26° south of east. D. 9.8 m at an angle of 64° south of east. E. 3.3 m at an angle of 26° south of east.
A copper sphere 2.5 cm in diameter is suspended by a fine wire in the center of an experimental hollow cylindrical furnace whose inside wall is maintained uniformly at 430°C. Dry air at a temperature of 90°C and a pressure of 1.2 atm is blown steadily through the furnace at a velocity of 14 m/s. The interior surface of the furnace wall is black. The copper is slightly oxidized, and its emissivity is 0.4. Assuming that the air is completely transparent to radiation, calculate for the steady state (a) the convection heat transfer coefficient between the copper sphere and the air, and (b) the temperature of the sphere.
GIVEN
• A copper sphere suspended in a furnace with air flowing over it
• Sphere diameter (D) = 2.5 cm = 0.025 m
• Sphere emissivity (?) = 0.4
• Furnace wall temperature (Tw) = 430°C = 703 K
• Air temperature (Ta) = 90°C = 363 K
• Air pressure (pa) = 1.2 atm
• Air velocity (U?) = 14 m/s FIND (a) The convective heat transfer coefficient ( ) ch (b) The temperature of the sphere (Ts) ASSUMPTIONS
• Steady state
• The air behaves as an ideal gas
• The furnace can be treated as a black body enclosure
• Only the density of the air varies with temperature
SKETCH
If you represented each star by a grain of sand, about how much sand would it take to represent all the stars in the observable universe?
A) all the sand in a typical playground sandlot B) all the sand on Miami Beach C) all the sand on the beaches of California D) one cubic meter of sand E) all the sand on all the beaches on Earth
Careful observations of nearby normal and active galaxies reveal that the ass of the central black hole is well correlated with the mass of the galactic bulge. The ratio of bulge mass to black hole mass is roughly:
A) 1 to 2000. B) 1 to 200. C) 1 to 20. D) 20 to 1. E) 200 to 1.