Question

A single Oreo cookie provides 53 kcal of energy. An athlete does an exercise that involves repeatedly lifting (without acceleration) a 100-pound weight two-feet above the ground with an energy efficiency of 25%. How many repetitions can she do with the energy supplied from a single Oreo cookie? What happens to the number of repetitions that can be done if the efficiency increases?

Answer 1

The number of times the athlete can lift the weight with single energy supplied by the Oreo cookie is 204 times and this number of times will increase if the efficiency increases.

Energy used by the athlete

The energy used by the athlete is calculated as follows;

E = Fd

where;

• F is the applied force = 100 lb weight = 444.82 N
• d is the distance = 2 ft = 0.61 m

E = 444.82 x 0.61 = 271.34 J

Input energy

The Input energy of the athlete = 53 kcal = 221752 J

Number of times the athlete can lift the weight

$E = \frac{0utput \ energy}{1nput \ energy} \\\\0.25 = \frac{n(271.34)}{221752} \\\\271.34n = 55483\\\\n = \frac{55483}{271.34} \\\\n = 204$

Thus, the number of times the athlete can lift the weight with single energy supplied by the Oreo cookie is 204 times and this number of times will increase if the efficiency increases.

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