H 120m
E
120m
60m
40m
F
A roller coaster begins at rest 120 m above the ground, as
shown. Assume no friction from the wheels and air, and that no
energy is lost to heat, sound, and so on. The radius of the loop
is 40 m. Find the speed of the roller coaster at points E and F.
Note:- Use
g= 10 m/s2

Under conditions for which the same room temperature is maintained by a heating or cooling system, it is not uncommon for a person to feel chilled in the winter but comfortable in the summer. provide a plausible explanation for this situation (with supporting calculations) by considering a room whose air temperature is maintained at 20â°c throughout the year, while the walls of the room are nominally at 27â°c and 14â°c in the summer and winter, respectively. the exposed surface of a person in the room may be assumed to be at a temperature of 32â°c throughout the year and to have an emissivity of 0.90. the coefficient associated with heat transfer by natural convection between the person and the room air is approximately 2 w/m2 â‹…â‹… k. what is the ratio of the thermal resistance due to convection to the thermal resistance due to radiation in the summer? what is the ratio of thermal resistances in the winter

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