Not long ago I was huffing and puffing on my bicycle up a very steep hill and another cyclist blew by me with apparently little effort. Now, in addition to looking younger, stronger, and having a better bicycle, he appeared to be carrying significantly less excess, ahem, baggage. So I got to wondering how much difference one’s weight (or to be charitable, a loaded backpack) makes when ascending a hill on a bicycle.
In the last two posts, we considered the units of food energy, and some of the issues associated with calculating human energy use. Today we’ll look at different views of calculating energy use from exercise.
Last post we talked about the units used for describing the energy content of food. For the purposes of an energy balance on the body, we also have to consider the efficiency of converting food energy into activity.
Sometimes it seems like most of the people you meet are on a diet of some kind—either to lose weight, gain weight, or stay the same. In any case, it seems reasonable to assume that diets ultimately have to be about the amount of energy that you take in as food or drink, and the amount of energy that your body burns through exercise or just existing. Today we’ll talk about the units used to measure energy in food.
We’ve talked before about the contact temperature and the effect that different materials have on the temperature that you feel when you first touch them. Today we’ll look at that effect in a more applied way.
If you live in an area with snow, you’ve probably experienced a snowfall followed by several cold clear days. If it lasted long enough, you may have noticed that the snow gradually starts to disappear (sublimate) even when the air temperature never gets above the melting point. In this post, we’ll look at the speed of that effect.
Last post we looked at another extension of lumped capacitance beyond our original exploration here and here. In the last post, we looked at a case where the heat transfer coefficient increased linearly with time, which might be a good approximation for the initial moments of the heat transfer for an object in a duct with the fan just starting up. Today we’ll look at a case where the heat transfer coefficient is decreasing.
Not long ago I was huffing and puffing on my bicycle up a very steep hill and another cyclist blew by me with apparently little effort. Now, in addition to looking younger, stronger, and having a better bicycle, he appeared to be carrying significantly less excess, ahem, baggage. So I got to wondering how much difference one’s weight (or to be charitable, a loaded backpack) makes when ascending a hill on a bicycle.