The tungsten filament of a light bulb has an operating temperature of about 2 100 k. if the emitting area of the filament is 1.0 cm2, and its emissivity is 0.68, what is the power output of the light bulb? (σ = 5.67 × 10−8w/m2⋅k4)
a. 100 wb. 75 wc. 60 wd. 40 w

75 W

Explanation:

= temperature of the filament = 2100 K

= Emitting area of the filament = 1 cm² = 10⁻⁴ m²

= Emissivity = 0.68

= Stefan's constant = 5.67 x 10⁻⁸ Wm⁻²K⁻⁴

Using Stefan's law, Power output of the light bulb is given as

initial speed when it is dropped is 150 ft/s

now at the same moment the acceleration due to gravity is perpendicular to its velocity

so as we know that

now we have centripetal acceleration a = 32 ft/s^2 as its perpendicular to velocity

while tangential acceleration at the same moment will be zero

so

now radius of curvature is given as

so the radius of curvature just after it is dropped is 703.125 ft