- #1
ShizukaSm
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An athlete needs to lose weight and decides to do it by "pumping iron". How many times must an 80 kg weight be lifted a distance of 1 m in order to burn off .5 kg of fat, assuming that that much fat is equivalent to 3500 Cal?
[itex]Q = n\left(m\cdot g \cdot h\right)[/itex]
[itex]3500\,10^3\,4.18=n\left(80\,9.8\,1\right)[/itex]
[itex]n = 18660.7 \text{ times}[/itex]
That was my book answer (as I imagined), but wouldn't it be more correct to assume that the athlete would use energy (the same energy) to lift iron up and then to support it down? Thus he would only need to lift it [itex]N = \frac{n}{2} = 9330.36[/itex]
I don't mean to be pedantic or anything like that, I'm genuinelly curious to know if it's physically correct to assume that.
[itex]Q = n\left(m\cdot g \cdot h\right)[/itex]
[itex]3500\,10^3\,4.18=n\left(80\,9.8\,1\right)[/itex]
[itex]n = 18660.7 \text{ times}[/itex]
That was my book answer (as I imagined), but wouldn't it be more correct to assume that the athlete would use energy (the same energy) to lift iron up and then to support it down? Thus he would only need to lift it [itex]N = \frac{n}{2} = 9330.36[/itex]
I don't mean to be pedantic or anything like that, I'm genuinelly curious to know if it's physically correct to assume that.