Question

A doughnut contains about 302 Calories. (Note: These are "food" Calories.) After eating this doughnut, you decide to compensate by taking the stairs instead of using the elevator. If each stair has a height of 22 cm, how many stairs must you climb to compensate for the doughnut? Assume all the energy in the doughnut can be converted to mechanical energy. (Take 75 kg as the mass of a typical person.)

Answer 1

Given that the energy contains in doughnut is Q = 302 Calories

                                                                       = 302x10³ cal

                                                                       = 302x10³ x4.19 J

                                                                       = 1265.38x10³ J          

(Since 1 Calorie is equal to 1000 cal)

Total energy required to reach height h is Q = mgh

                                                             h = Q /mg

                                                                = 1265.38x10³ J / 75kg*9.8m/s²       

                                                                = 1.7216x10³ m

But height of the each step is h' = 22cm = 0.22m

Number of stairs that you climb is

                    N = h /h'

                        = 1.7216x10³ m / 0.22m

                        = 7.825x10³

                        = 7825 steps