posted by hilary .
Nate is 165 cm tall, 40 cm wide, and weighs 710 N. He needs to walk ten blocks (1000 m) against a 50 km/h head-wind.
Nate pushes on the ground with the minimum force that allows him to move slowly forward at a constant speed, and against the drag from the wind.
How much energy does Nate spend?
You need to estimate the wind drag force based upon his projected area. That area is 1.65 x 0.40 = 0.66 m^2
The drag force is approximately
(1/2)*(body area)*(air density)*(headwind speed)^2
The air density is about 1.2 kg/m^3
His weight will not matter except for a basic metabolism energy burning rate, which they did not ask for.
Multiply the drag force (in Newtons) by the distance traveled (1000 m) for the energy (work) required, in Joules.
There is no exact answer to this one. Drag coefficients depend upon shape; I used a value of 1.