Human efficiency (Physics calculations)

Discussion in 'General Discussion' started by FreeStream, 13 May 2006.

1. FreeStream

Posts: 13,320

Now, a team of around 4 people have lifted 4298 kg 4.5 meters into a cargo hold.

Joules = weight x distance moved

4298x10=42980 Newtons
42980x4.5=193410 Joules or 193.41kJ.

Over 4 people thats 48.3525kJ each. This is all rough

Now, a slice of bread is ruffly 500kJ, so we cant have used 10% of a slice of bread each to lift 1 ton each.

Even if we are 10% efficient, thats still a slice of bread to life 1 ton. Unless we are less than 1% efficient, that doesn't seem right to me

So, what am I doing wrong

2. Ricochet J

Posts: 12,890

Yes but you have to realise Energy comes from other places in our body too, if my memory serves me correctly, through both aerobic and anerobic respiration

3. FreeStream

Posts: 13,320

But surely the food energy (chemical) is used abit to respire?

No food = no energy = dead?

4. Ricochet J

Posts: 12,890

Glucose + Oxygen = Carbon Dioxide + Water + Energy

Glucose comes from many sources, not just food. And off course oxygen is oxygen. The products are Co2, H20 and Kj

Edit: Even if the food was supplying the Glucose the body would use Glucose reserves in the Gall Bladder (I think it's stored there) for anerobic respiration.

Edit 2: For anerobic respiration, Glucose ---> Lactic Acid + Energy. The lactic acid builds up in the muscles when using reserves, that is why your muscles feel like rubber and feel a burning sensation when doing something active like sport or going to the gym

Last edited: 13 May 2006
5. FreeStream

Posts: 13,320

Yeee , I pretty much knew all that BUT the glucose first came from a food source. So now its in the body, what is the efficiency?

Eg. Eat, then start lifting/running/exercise, what % of that energy in the food is used to lift/propell you?

CR.

6. Ricochet J

Posts: 12,890

We need a Biologist. All this stuff that's coming out of my mouth is my GCSE biology days.
I am now an A Level Physicist!

7. FreeStream

Posts: 13,320

Im coming to the end of my GCSEs, going on to A level Physics (got A* in mocks in Physics lol - Maths and geography

8. Ricochet J

Good stuff