A 30 kg male emperor penguin under a clear sky in the Antarctic winter loses very little heat to the environment by convection; its feathers provide very good insulation. It does lose some heat through its feet to the ice, and some heat due to evaporation as it breathes; the combined power is about 12 W. The outside of the penguin's body is a chilly −22∘C, but its surroundings are an even chillier −38∘C. The penguin's surface area is 0.56 m2, and its emissivity is 0.97. What is the rate of energy loss by radiation

Rate of energy loss by radiation is 28.31 Watt

Explanation:

Given that;

m = 30 kg

power p = 12 W

emissivity e = 0.97

Surface Area A = 0.56 m²

outside of the penguin's body  T = −22°C

surroundings Temperature Ts = -38°C

the rate of energy loss by radiation = ?

Now, using Stefan-Boltzmann law;

P = σeA [ T⁴ - Ts⁴ ]

Stefan's constant σ = 5.67 × 10⁻⁸

so we substitute

P = 5.67 × 10⁻⁸ × 0.97 ×  0.56  [ (-22 + 273 k)⁴ - (-38 + 273 k )⁴]

= 3.079944 × 10⁻⁸ [ 919325376]

=  28.31 Watt

the rate of energy loss by radiation is 28.31 Watt

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s