Science/energy problem?

Question

Ok, so I have this science problem that I'm not too sure about, if you can help, than thank you! Working out would be nice.

So, the problem is:

How many bicep curls with a 1 kg weight would burn off a 100g Marsbar/chocolate bar?

The chocolate bar has 1920kJ per 100g.

Thanks again!

Answer 1

Lets say each curl raises the bar 0.5 m (that's an overestimate unless you have huge forearms).  The energy required for each lift is:

E(lift) = mass * distance * acceleration of gravity = 1 kg*0.5m*9.8m/s^2

        = 4.9 joules/lift = 0.0049 kJ/lift

Since there are 1920 kJ in a chocolate bar, you need around 400,000 lifts to work off the calories (1920 kJ / 0.0049 kJ/lift).