What were the first celestial bodies added to our solar system inventory by Galileo and his telescope? Why were they important?
What will be an ideal response?
The four moons of Jupiter showed that other planets had satellites like our Moon, making us just one of the worlds orbiting the still larger Sun.
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In a metal alloy manufacturing and heat treatment plant and in its immersion quenching process, steel plates are first heated in a furnace and then quenched (or cooled) in a coolant bath to obtain the desired steel properties and surface hardness. In one such process a flat stainless steel plate 0.6-cm-thick, 7.5-cm-wide and 0.3-m-long is immersed horizontally at an initial temperature of 980°C in a large water bath at 100°C and at atmospheric pressure. Determine how long it will take this plate to cool to 540°C.
GIVEN
? A flat stainless steel plate is immersed horizontally in water
? Plate thickness (s) = 0.6 cm = 0.006 m
? Plate width (w) = 7.5 cm = 0.075 m
? Plate length (L) = 0.3 m
? Initial plate temperature (Tpi) = 980°C = 1253 K
? Pressure = 1 atm
? Water bath temperature (Tb) = 100°C (saturation) = 373 K
FIND
? Time for plate to cool to Tpf = 540°C = 813 K
ASSUMPTIONS
? The heat fluxes from the bottom and top of the plate are equal
? The plate is polished
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 13, for water at the pool temperature of 100°C
From Appendix 2, Table 35, for steam at 100°C
From Table 9.2, The surface tension, o, for water @ 100°C = 0.0589 N/m
From Table 9.1, The coefficient, Csf, for water on mechanically polished stainless steel = 0.0132
From Table 11.3, the emissivity of polished stainless steel at the average temperature of
(980°C + 540°C)/2 = 760°C (g) = 0.22
Which gases within our atmosphere act as greenhouse gases?
a. water b. carbon dioxide c. oxygen and nitrogen d. all of the above e. a and b
Given that the wavelengths of visible light range from 400 nm to 700 nm, what is the highest frequency of visible light? (c = 3.0 x 108 m/s)
A) 3.1 × 108 Hz B) 7.5 × 1014 Hz C) 2.3 × 1020 Hz D) 4.3 × 1014 Hz E) 5.0 × 108 Hz
What is the simplest way we might detect life on an extrasolar planet?
A) listen for radio signals coming from an advanced civilization on the planet B) wait for aliens from the planet to visit us C) analyze the spectrum of reflected light from the planet D) send an interstellar probe to the planetary system