question_answer 28)

                  A person of mass 60 kg wants to lose 5 kg by going up and down a 10 m high stairs. Assume lie burns twice as much fat while going up than coining down. If 1 kg of fat is burnt on expending 7000 kilo calories, how many times must lie go up and down to reduce his weight by 5 kg?                

Answer:

                  Energy to be expend to burn 5 kg fat                 \[=5\times 7000\times {{10}^{3}}\text{ cal}\]                 \[=35\times {{10}^{6}}\times 4.2\text{ }J\text{ }=\text{ }147\times {{10}^{6}}J\]                 Let lie completes N up and down to expend this energy                 \[\therefore \] Total energy to be expend in N up and down motions = nigh \[\times \] N                 \[=60\times 10(10+5)N\]                 \[=60\times 10\times 15\text{ }N=(900\,N)J\]                 \[\therefore \]  \[900\text{ }N=147\times {{10}^{6}}\]                 or \[N=\,\frac{147\times \,{{10}^{6}}}{900}\,=\,16.3\,\,\times \,{{10}^{4}}\]