A 72.0 kg person is put on an exercise program by a physical therapist, the goal

Question

A 72.0 kg person is put on an exercise program by a physical therapist, the goal being to burn up 600 food calories in each daily session. Recall that human muscles are about 20.0 % in converting the energy they use up into mechanical energy. The exercise program consists of a set of consecutive high jumps, each one 50.0 cm into the air (which is pretty good for a human) and lasting 1.50 s, on the average.

a) How many jumps should the person do per session?

b) How much time should be set aside for each session?

Please help and also explain.

Explanation / Answer

the goal being to burn up 600 food calories: => total mechanical energy = 20 % of 600 = 1/5 * 600 = 120 >>>> total energy spent should be = 120 * 4186 J = 502320 J ------------------------------------------------------------ energy lost per jump = mgh = 72 * 9.8 * 0.50 = 352.8 J number of jumps = 502320/352.8 = 1423.81 = 1424 jumps per session Each jump is of 1.5 s => total time = 1424*1.5 s = 2136 sec = 35.6 mins

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