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Energy of locomotion. On flat ground, a 70 - kg person requires about 300 W of metabolic power to walk at a steady pace of 5 -km/hr (1.4 m/s). Using the same metabolic power output, that person can bicycle over the same ground at 15 - km/h.

How many times greater is the kinetic energy of the person when biking than when walking? Ignore the mass of the bike. (a) 1.7; (b) 3; (c) 8; (d) 9

Short Answer

Expert verified

The correct answer is option (d).

Step by step solution

01

Identification of given data

The mass of the person is m = 70 kg.

The velocity of walking is vwalking=5km/h.

The velocity of cycling is vcycling=15km/h.

The metabolic power is P = 300 W.

02

Concept/Significance of kinetic energy

The expression of kinetic energy is given by,

K=12mv2

Here, m is the mass of the body, and v is velocity of the body.

03

Determine the number of times the kinetic energy of the person when biking than when walking

Take the ratio of kinetic energy of a person in cycling and walking.

KcyclingKcycling=12mv2cycling12mv2walking=v2cyclingv2walking=15km/h25km/h2=9

Simplify further.

Kcycling=9Kwalking

Therefore, the kinetic energy of a person in cycling is times greater than walking.

Thus, the options (a), (b), and (c) are incorrect.

Hence, the correct answer is option (d).

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