Solve Fusion & Einstein Homework: Energy Output & Mass Conversion

[Sastronaut]

Homework Statement

The energy output of an average person is about 121 Watts. Suppose the average human has a mass of 80 kg and it could run on fusion power by converting only .7% of its mass into energy.
1) how much energy would be available to the body through fusion?
2) How long could the body operate on fusion power (in years)?

Homework Equations

E=mc²

The Attempt at a Solution

Question involves 1)...i completed the problem, but realized that i may have made an error. in the first step i multiplied 80kg by .007 or .7% to get a value of .56 kg that could be used in fusion. I then plugged that into E=mc^2 and calculated a value of 5.04x10^16 J. Now does anyone think that for one i am instead being asked to calculate what energy is available if the average human could use its whole weight (80Kgs) in fusion? The rest of my work is bellow i would greatly appreciate if someone could give it a once over! thanks pf!


unknown burned = 121W/5.04x10^16J/kg = approx. 2.401x10^-15 kg/s

lifetime=(1.00)(80kg/2.401x10^-15 kg/s) = approx. 3.332x10^16s

answer: 1.06x10^9 years

 

[Simon Bridge]

Now does anyone think that for one i am instead being asked to calculate what energy is available if the average human could use its whole weight (80Kgs) in fusion?

Relax - the problem is assuming that 80kg of hydrogen fuel is available to power the body.
In 4H->He fusion, only 0.7% of the proton mass is converted to energy - then all the fuel is converted into He: none left to burn.