Register to reply

How do you find out energy required per day?

by Avichal
Tags: energy, required
Share this thread:
Avichal
#1
Aug20-13, 06:34 AM
P: 283
Human body needs about 2000-2500 calories per day. How do you find out this number?
What sort of experiments do people do to figure out this number?

Also, in general how do you find things like - energy spent while walking, talking, blinking? It almost seems impossible to find out these things but I find numbers in books.
Phys.Org News Partner Medical research news on Phys.org
Viral therapy could boost limb-saving cancer treatment
Middle East Respiratory Syndrome coronavirus detected in the air of a Saudi Arabian camel barn
Schizophrenia's genetic 'skyline' rising: Suspect common variants soar from 30 to 108
mfb
#2
Aug20-13, 09:07 AM
Mentor
P: 11,573
Some things you can try:
- measure the produced heat of the body during those activities (and at rest)
- measure the required oxygen, as this is related to the consumed energy
- measure the required food (long-term measurement)
- use some model of the muscles to find an estimate
- probably some concepts I forgot or do not know
Avichal
#3
Aug20-13, 11:26 AM
P: 283
I find it extremely hard to believe that you can actually calculate energy we require for doing activities. There are just too many things involved. Does this actually work?

mfb
#4
Aug20-13, 12:10 PM
Mentor
P: 11,573
How do you find out energy required per day?

It is possible to find approximations. The actual power/energy will vary a bit between different persons, details of the activity and other circumstances. And you always have a measurement uncertainty, of course.
It is just interesting how precise those values are. To find some values is easy.
Avichal
#5
Aug20-13, 12:30 PM
P: 283
Just for the sake of an example, say I want to calculate energy it takes for an average man to climb 30 stairs (30 steps).
I just calculated using E = m.g.h. Will that be a correct approximation? Why/why not?
mfb
#6
Aug20-13, 03:01 PM
Mentor
P: 11,573
It is a lower limit. The human body is far away from 100% efficient.
Ryan_m_b
#7
Aug20-13, 04:27 PM
Mentor
Ryan_m_b's Avatar
P: 5,400
There will also be other complications like the fitness of the person in question. An unfit person will take longer to return to a basal (resting) metabolic state so in addition to the energy expended climbing the stairs there's the period after characterised by faster heart rate, heavy breathing etc.
Borek
#8
Aug20-13, 04:33 PM
Admin
Borek's Avatar
P: 23,363
How is it different from measuring heat of any process? Technically you just use a larger calorimeter (think thermally isolated room). I believe that's how the early experiments were designed.


Register to reply

Related Discussions
Find energy required to keep a rope oscillating Introductory Physics Homework 1
Please Help me to find HP of electrical Motors Required Engineering Systems & Design 0
Find the minimum time required to go a given distance Introductory Physics Homework 0
Delat energy required to excite hole from lowest energy orbit to valence band? Atomic, Solid State, Comp. Physics 1
Fluid Mechanics - Find the required power Engineering, Comp Sci, & Technology Homework 0