General > General Technical Chat
Physics Question - ma = mg
TimFox:
From my younger days, I remember Resnick and Halliday as having very well written explanations on the basic topics for freshmen who could do elementary calculus.
CatalinaWOW:
--- Quote from: TimFox on July 03, 2021, 08:23:35 pm ---From my younger days, I remember Resnick and Halliday as having very well written explanations on the basic topics for freshmen who could do elementary calculus.
--- End quote ---
The first several chapters don't even require calculus. The text is written assuming that the course is concurrent with first year calculus.
bostonman:
--- Quote ---Think of your body as a very inefficient car. It burns something like 1000-1500 calories a day sitting in a chair doing nothing. The work perform lifting a weight or walking a treadmill is almost negligible.
--- End quote ---
Ignoring for a moment that apparently Newtonian work is different than biological, I'm uncertain I agree with this statement. If someone has a desk job, and the best they can burn is 1500 calories, ninety-minutes on the treadmill burning 300 plus calories is 20% or more additional burnt calories. That could mean the difference of burning off your lunch, or not.
As for thinking I could use lifting an object to calculate calories burned, guess I need to research this.
TimFox:
Warm-blooded mammals need to consume energy in order to maintain their body temperature and vital processes, hence the energy consumption at rest and that one can starve to death while totally sedentary.
Again, another misnomer in units: when dietitians say "calories", they mean "kilocalories". Neither are SI units, since heat energy and other energy forms are equivalent and are measured in Joules.
The "calorie" is defined as the amount of heat energy that will raise the temperature of one gram of water by one Kelvin. Similarly, the "kilocalorie" or "kilogram-calorie" or "large calorie" is the energy required to raise the temperature of one kilogram of water by one Kelvin. These units are convenient when doing wet chemistry. Confusion between small-c and large-C calories persists amongst non-physicists and is enough reason to use Joules for serious work. At least the BTU is well-defined.
ucanel:
Great video that discusses the subject:
(in a funny way also)
Science Ashlyum
Why did i take a scale on an elevator?
https://youtu.be/c6KliNGReTQ
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