The winning time for the 2005 annual race up 86 floors of the Empire State Building was 10 min and 49 s . The winner's mass was 60 kg . If each floor was 3.7 m high, what was the winner's change in gravitational potential energy? If the efficiency in climbing stairs is 25 %, what total energy did the winner expend during the race? How many food Calories did the winner "burn" during the race? What was the winner's metabolic power in watts during the race up the stairs? Express your answer using two significant figures.

Respuesta :

Answer:

[tex]1.9\times 10^5\ J[/tex]

[tex]1.8\times 10^{2}\ kcal[/tex]

[tex]1.3\times 10^{2}\ kcal[/tex]

[tex]1.2\times 10^{3}\ W[/tex]

Explanation:

m = Mass of person = 60 kg

g = Acceleration due to gravity = 9.81 m/s²

t = Time taken = 10 min and 49 s

Total height

[tex]h=3.7\times 86\\\Rightarrow h=318.2\ m[/tex]

Potential energy is given by

[tex]U=mgh\\\Rightarrow U=60\times 9.81\times 318.2\\\Rightarrow U=187292.52\ J[/tex]

The gravitational potential energy is [tex]1.9\times 10^5\ J[/tex]

The energy in the climb

[tex]\dfrac{187292.52}{0.25}=749170.08\ J[/tex]

Converting to kcal or Cal

[tex]\dfrac{749170.08}{4184}=179.05594\ kcal[/tex]

The amount of energy used to climb [tex]1.8\times 10^{2}\ kcal[/tex]

Amount gone to heat

[tex]179.05594\times 0.75=134.291955\ kcal[/tex]

The amount burned [tex]1.3\times 10^{2}\ kcal[/tex]

Power is given by

[tex]P=\dfrac{E}{t}\\\Rightarrow P=\dfrac{749170.08}{10\times 60+49}\\\Rightarrow P=1154.34526\ W[/tex]

The power is [tex]1.2\times 10^{3}\ W[/tex]