Question #390
The recording below was obtained from a subject connected to a spirometer filled with pure oxygen while cycling on a bicycle ergometer. A carbon dioxide absorber was present in the system. The diameter of the bicycle wheel was one metre and it turned twice each second. Against what force was the subject peddling?
Take pi to be 3.
During exercise the subject has a power output of 60 W, i.e. does 60 J of work each second.
The effective distance travelled per second depends on the the circumference of the bicycle wheel and the number of revolutions it makes per second. Its circumference is pi x d, i.e. 3 x 1 = 3 m. It makes two revolutions per second and thus the effective distance travelled is 6 m / s.
Work done = force x distance, so force = 60 / 6 = 10 N.