A football is thrown upward at a 30.0° angle to the horizontal. To throw a 40.0-m pass, what must be the initial speed of the ball?
21.3 m/s
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A 4-cm-diameter cylindrical enclosure with black surfaces, as shown in the accompanying sketch, has a 2-cm hole in the top cover. Assuming the walls of the enclosure are at the same temperature, determine the percentage of the total radiation emitted from the walls that escapes through the hole in the cover.
GIVEN
• Cylindrical enclosure of black surfaces shown above
• Cylinder diameter (D) = 4 cm = 0.04 m
• Diameter of hole in top (Dh) = 2 cm = 0.02 m
FIND
• The percentage of the total radiation emitted from the wall which will escape through the hole in the cover (Fe4).
ASSUMPTIONS
• The walls of the enclosure are at the same temperature
What aspect of Kepler's theory would have horrified all astronomers before Kepler?
A) Kepler's elliptical orbits. B) The fact that the Earth has a spherical shape in Kepler's theory. C) Kepler's simple circular orbits. D) The fact that Earth was no longer at the center. E) The absence of any epicycles [or "circles-within-circles"].
Gamma radiation is the highest frequency of EM waves
a. True b. False Indicate whether the statement is true or false
A Carnot heat engine could have an efficiency of 100% only if the temperature of the exhaust were at ________.
What will be an ideal response?