The tungsten filament of an electric lamp has a length of 0.5 m and a diameter 6x10m. The power rating of the lamp is 60 W. Assuming the radiation from the
filament is equivalent to 80%
that of a perfect black body radiator at the same
temperature, estimate the steady temperature of the filament.
(Stefan constant -5.7x10 %WmrK')

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.