Astar with the same mass and diameter as our sun rotates about a central axis with a period of 28.8 days. suppose that this star runs out of nuclear fuel and collapses to form a white dwarf star with a diameter equal to that of the earth. assume the star acts like a solid sphere, that there is no loss of mass in the process, and that the star has no external torques acting on it. as gravity causes the star to contract, gravitational potential energy is converted to rotational kinetic energy, so kinetic energy is not conserved. the radius of the sun is 6.96×108 m, and the radius of the earth is 6.37×106 m. (a) what would be the rotation period of the new white dwarf

Aman does 500 j of work pushing a car a distance of 2 m. how much force does he apply? assume there is no friction. a. 250 n b. 1000 n c. 125 n d. 500 n

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

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