A laser produces a beam of 4000-nm light. A shutter allows a pulse of light, 30 ps in duration, to pass through
What is the uncertainty in the energy of a photon in the pulse? (1 eV = 1.60 × 10-19 J, h = 6.626 × 10-34 J ? s)
A) 2 ×10-5 eV B) 2 ×10-6 eV C) 2 ×10-4 eV D) 2 ×10-3 eV E) 2 ×10-2 eV
A
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Consider a heat treatment process in which steel rods with a 10 cm diameter at an initial temperature of 600°C are inserted into an oil bath at 25°C. Assuming a convection coefficient of 400 W/(m2 K) between the oil and the rod, estimate how long it takes for the centerline of the rod to cool to 60°C. If the steel rod, which is 1 m long, is withdrawn from the bath at this point in the process, i.e., when the centerline temperature has reached 60°C, estimate the rate at which heat must be extracted from the oil to maintain its temperature constant during the process of treating 25 rods per hour.
GIVEN
• Heat treatment of steel rod inserted in oil bath
• Rod outside diameter = 0.1 m
• Initial temperature (T0) = 600°C
• Oil bath temperature (T?) = 25°C
• The average heat transfer coefficient ch = 400 W/(m2 K)
FIND
• Time it takes for centerline of the rod to cool to 600C.
• Rate at which heat must be extracted from oil to maintain its temperature constant during the process of treating 25 rods per hour.
ASSUMPTIONS
• Radial conduction only in billet
• Uniform and constant properties
SKETCH
Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude?
A) Rigel has a higher surface temperature than Sirius. B) Rigel has a higher core temperature than Sirius. C) Sirius has a higher core temperature than Rigel. D) Sirius has a higher surface temperature than Rigel.
Jupiter's magnetic field is the result of ________.
A. huge storms in its upper atmosphere generating lightning B. an aurora in its upper atmosphere C. the alternating wind directions in its atmosphere D. its rapid rotation and convective interior E. the large amount of iron present in its interior
You are at the leading end of a canoe and your friend is at the trailing end while the canoe is drifting along at a speed v. You toss a backpack to your friend. While the backpack is in flight, what is the canoe's speed? Ignore any friction effects between the canoe and the water
1.It is greater than v. 2.It is less than v. 3.It maintains the same speed it had before the backpack was thrown. 4.We cannot tell from the information given.