A typical doughnut contains 2.0g of protein, 17.0g of carbohydrates, and 7.0g of

Question

A typical doughnut contains 2.0g of protein, 17.0g of carbohydrates, and 7.0g of fat. The average food-energy values of these substances are 4.0kcal/g for protein and carbohydrates and 9.0kcal/g for fat.

Part A

During heavy exercise, an average person uses energy at a rate of 510kcal/h. How long would you have to exercise to "work off" one doughnut?

Express your answer using two significant figures.

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Part B

If the energy in the doughnut could somehow be converted into the kinetic energy of your body as a whole, how fast could you move after eating the doughnut? Take your mass to be 60kg, and express your answer in m/s.

Express your answer using two significant figures.

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Part C

Express your answer in km/h.

Express your answer using two significant figures.

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Solition:

Total energy due to protein and carbo hyfdrates = m1 = q1 =(2+17)(4 ) = 76 x 10^3 cal

Energy due to fat = q2 = 7 x 9 x 10^3 = 63 x 10^3 cal

Total energy = Q=q1+q2 = (76+63)x10^3 =139 x 10^3 cal

The power = rate of using energy = P = 510 kcal/h = 592 j/s

Power = energy / time

=> Time = t = 139 x 10^3 /510 x10^3 hours = 0.27 hours =16 min

B) To convert this energy to kinetic energy:

1/2* 60 * v^2 = 139 * 4.18 J

=>v^2 = 2 x 581/60 = 19.4

=>v = 4.4 m/s

1km = 1000m and 1 h =3600 s

=> velocity = 16 km/h

Comment

B and C are not correct

A typical doughnut contains 2.0g of protein, 17.0g of carbohydrates, and 7.0g of fat. The average food-energy values of these substances are 4.0kcal/g for protein and carbohydrates and 9.0kcal/g for fat.

Part A

During heavy exercise, an average person uses energy at a rate of 510kcal/h. How long would you have to exercise to "work off" one doughnut?

Express your answer using two significant figures.

t = min

SubmitMy AnswersGive Up

Part B

If the energy in the doughnut could somehow be converted into the kinetic energy of your body as a whole, how fast could you move after eating the doughnut? Take your mass to be 60kg, and express your answer in m/s.

Express your answer using two significant figures.

v =   m/s

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Part C

Express your answer in km/h.

Express your answer using two significant figures.

v =   km/h

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Explanation / Answer

B) total energy is 139*10^3 cal and not simply 139 cal

so converting 139*10^3 cal into KE

KE = 0.5*m*v^2 = 139*10^3*4.186 = 581854 J

0.5*m*v^2 = 581854

v^2 = 581854/(0.5*60)

v = 139.3 m/s

C) 139.3 m/s = 139.3*18/5 = 501.48 km/h

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