Energy conversion- burning wood to lifting an object

[jongood]

Homework Statement

If the calorific value of wood is 16 MJ/kg and a match weights approximately 0.17 g, then (a)
how much energy (in joules) is released by burning the wooden part of a single match? If all
of this energy were applied to do work to lift a 60 kg human vertically, against gravity, then
(b) how high could the person be lifted?

Homework Equations

W=F*d

F=ma

The Attempt at a Solution

So for a. I was given the calorific value for a kg of wood. So I crossed multipled and divide.

(16 MJ/kg*.00017kg) /1= 2720 J

then for B.

Joules can also be expressed in Nm
using formula W=F*d ->W/F=d

I was confused at first about the 80 kg because I assumed that was his weight but I am using that number as his mass. So found out that 80kg of mass= 588 N

w=2720Nm F= 588 N

2720Nm/588N= 4.626 m

Now does that seem a lot to you? It did at first but now I am not sure.

Please let me know if I am on the right track. This whole answer hinges on if I got the first part right... it seemed too easy so that's why i am second guessing myself...

 

[gneill]

Looks good. Lot's of energy bound up in organic substances, which is why we burn coal and oil for energy.

 

[bluesurge863]

Yes, it seems reasonable. That's the problem with heat - there's a whole lot of it, but we can utilize only small fractions to make it do what we want.

 

[rude man]

Yeh - darn Carnot, Clausius & Kelvin and their 2nd law!

 

[DeeNos]

I can confirm that your calculations are correct. Burning wood releases a significant amount of energy, and using that energy to lift a 60 kg human vertically against gravity can result in a height of 4.626 meters. It is important to note that this is a theoretical calculation and in reality, there would be energy losses due to friction and other factors. Nonetheless, your understanding of the concepts and application of the equations is correct. Keep up the good work!