Question
2. Using data from Table, calculate the daily energy needs of a person who sleeps for 8.00 h, walks
for 2.00 h, works in the office for 8 hours, does moderate physical work during 2 hours and lying awake
for 4 hours. (suppose, that working in office consumes energy at the same rate as sitting upright.). Suppose
that the person mass is 80-kg and his height 1.75m.
expand button
Transcribed Image Text:2. Using data from Table, calculate the daily energy needs of a person who sleeps for 8.00 h, walks for 2.00 h, works in the office for 8 hours, does moderate physical work during 2 hours and lying awake for 4 hours. (suppose, that working in office consumes energy at the same rate as sitting upright.). Suppose that the person mass is 80-kg and his height 1.75m.
1. First law of thermodinamics AQ = AU + AW
The first law of thermodynamics is a version of the law of conservation of energy The first law is often
formulated by stating that the change in the internal energy AU of a closed system is equal to the amount
of heat supplied to the system AQ, minus the amount of work done AW by the system on its
surroundings.
Units of work and energy are Joules(J) and calories (cal).
Relationship between units 1 cal = 4.18 J and 1 Cal = 1000 cal = 4180 J
Kinetic energy (J): KE = , here m is mass of a body (kg), v – speed of its motion(m/sec).
2.
3. Gravitational potential energy(J): PE = mgh, here m is mass of the body (kg); g = 9,8 m/sec? is
acceleration due to gravity; h is height (m).
Work W (J):
4.
Formally, the work done on a system by a constant force is defined to be the product of the component
of the force in the direction of motion times the distance through which the force acts. For one-way motion
in one dimension, this is expressed in equation form as:
W = FAxcos0 , where W is work, Ax is the displacement of the system, and 6 is the angle between the
force vector F and the displacement vector Ax.
5. Work – Energy theorem: The principle of work and kinetic energy (also known as the work-energy
theorem) states that the work done by the sum of all forces acting on a particle equals the change in the
kinetic energy of the particle: W = AKE = "-i, here v, is final velocity and v; is initial velocity.
Let us calculate the work done in lifting an object of mass m through a height h. If the object is lifted
straight up at constant speed, then the force needed to lift it is equal to its weight mg. The work done on
the mass is: W = APE = mgAh, here m is mass of the body (kg); g = 9,8 m/sec? is acceleration due to
gravity; Ah is change in height.
6. Power P (W) is rate at which work is done: P = ", where W is work (J) and t is time.
7. Efficiency Even though energy is conserved in an energy conversion process, the output of useful
energy or work will be less than the energy input. The efficiency n of an energy conversion process is
defined as 1 =
- where W is useful energy or work output, E is total energy input, Q is heat or thermal
w-Q
energy.
8. Energy conversion in humans
Our own bodies, like all living organisms, are energy conversion
machines. Conservation of energy implies that the chemical
energy stored in food is converted into work, thermal energy,
and/or stored as chemical energy in fatty tissue. The fraction
going into each form depends both on how much we eat and on
our level of physical activity. If we eat more than is needed to
do work and stay warm, the remainder goes into body fat.
carbohydrates and proteins K1 = 17,2 kJ/g =4.11 Cal/g
fat K2 = 38,9 kJ/g=9.3 Cal/g.
W (negative)
Work
OE
Food
Thermal
energy
energy
OE,
Stored
fat
OE, + W = OE,
expand button
Transcribed Image Text:1. First law of thermodinamics AQ = AU + AW The first law of thermodynamics is a version of the law of conservation of energy The first law is often formulated by stating that the change in the internal energy AU of a closed system is equal to the amount of heat supplied to the system AQ, minus the amount of work done AW by the system on its surroundings. Units of work and energy are Joules(J) and calories (cal). Relationship between units 1 cal = 4.18 J and 1 Cal = 1000 cal = 4180 J Kinetic energy (J): KE = , here m is mass of a body (kg), v – speed of its motion(m/sec). 2. 3. Gravitational potential energy(J): PE = mgh, here m is mass of the body (kg); g = 9,8 m/sec? is acceleration due to gravity; h is height (m). Work W (J): 4. Formally, the work done on a system by a constant force is defined to be the product of the component of the force in the direction of motion times the distance through which the force acts. For one-way motion in one dimension, this is expressed in equation form as: W = FAxcos0 , where W is work, Ax is the displacement of the system, and 6 is the angle between the force vector F and the displacement vector Ax. 5. Work – Energy theorem: The principle of work and kinetic energy (also known as the work-energy theorem) states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle: W = AKE = "-i, here v, is final velocity and v; is initial velocity. Let us calculate the work done in lifting an object of mass m through a height h. If the object is lifted straight up at constant speed, then the force needed to lift it is equal to its weight mg. The work done on the mass is: W = APE = mgAh, here m is mass of the body (kg); g = 9,8 m/sec? is acceleration due to gravity; Ah is change in height. 6. Power P (W) is rate at which work is done: P = ", where W is work (J) and t is time. 7. Efficiency Even though energy is conserved in an energy conversion process, the output of useful energy or work will be less than the energy input. The efficiency n of an energy conversion process is defined as 1 = - where W is useful energy or work output, E is total energy input, Q is heat or thermal w-Q energy. 8. Energy conversion in humans Our own bodies, like all living organisms, are energy conversion machines. Conservation of energy implies that the chemical energy stored in food is converted into work, thermal energy, and/or stored as chemical energy in fatty tissue. The fraction going into each form depends both on how much we eat and on our level of physical activity. If we eat more than is needed to do work and stay warm, the remainder goes into body fat. carbohydrates and proteins K1 = 17,2 kJ/g =4.11 Cal/g fat K2 = 38,9 kJ/g=9.3 Cal/g. W (negative) Work OE Food Thermal energy energy OE, Stored fat OE, + W = OE,
Expert Solution

Want to see the full answer?

Check out a sample Q&A here
Blurred answer
Students who’ve seen this question also like:
College Physics
College Physics
11th Edition
ISBN: 9781305952300
Author: Raymond A. Serway, Chris Vuille
Publisher: Cengage Learning
Not helpful? See similar books
College Physics
College Physics
Units, Trigonometry. And Vectors. 1CQ
marketing sidebar icon
Want to see this answer and more?
Experts are waiting 24/7 to provide step-by-step solutions in as fast as 30 minutes!*
*Response times may vary by subject and question complexity. Median response time is 34 minutes for paid subscribers and may be longer for promotional offers.

Related Physics Q&A

Find answers to questions asked by students like you.

Q: 2. How long must a 100-W light bulb run in order to consume a million joules of electrical energy?…

A: (2)    Given data:                      Power (P) = 100 W                      Electrical Energy (E)…

Q: 9.A fan is to accelerate quiescent air to a velocity to 12 m/s at a rate of 3 m°/s. If the density…

A: Given data: Velocity of air, v=12 m/s Density of air, ρ=1.15 kg/m3 Volume flow rate, V˙=3 m3/s

Q: A 70 kg climber ascends a slope until reaching a height difference of 1200 m in 3 hours:  Assuming…

A: Click to see the answer

Q: 15. Refer to the graph below. Calculate the total work done from t = 0.00m to t= 8.00 me 12 10 2 Ar…

A: The area under the curve of the force v/s displacement graph gives the work done.

Q: 5) The maximum energy a bone can absorb without breaking is surprisingly small. For a healthy human…

A: Assume that the man and the Earth is an isolated system, so there is no heat transfer is occurs.

Q: Your 1,221 kg car, moving at 6 m/s, approaches the bottom of a hill that is 24 m high. To save fuel,…

A: Click to see the answer

Q: A 220-lb man jumps out a window into a fire net 36 ft below. The net stretches 4.4 ft before…

A: Click to see the answer

Q: 41. The second floor of a house is 6 m above the street level. How much work is required to lift a…

A: Mass of refrigerator (m) = 300 kg  Height of second floor (h) = 6 m

Q: 5.) A skydiver, mass 60 kg, jumps out of an airplane traveling 65 m/s horizontally at an altitude of…

A: Work energy theorem will be applied here.

Q: The energy we require to live comes from the chemically stored potential energy in food, which is…

A: Click to see the answer

Q: The record time for a Tour de France cyclist to ascend the 1100-m-high Alpe d'Huez is 37.5 min. The…

A: Click to see the answer

Q: 3. Determine the mass of a bungee jumper with potential energy of 2,970 J if the height of the…

A: Given: The height jumping platform is 62 m. The potential energy of the jumper is 2970 J.

Q: 30) At what minimum rate is a 60.0-kg boy using energy when, in 8.00 s, he runs up a flight of…

A: The boy will definitely gain some energy while climbing the stairs that are 10 m high. Now, as this…

Q: A 58.0 kg cheetah accelerates from rest to its top speed of 33.3 m/s. HINT (a) How much net work (in…

A: . (a) work done is equal to change in kinetic energy. that is, W=12mv2-12mu2u=0W=12mv2W=1258.0…

Q: 1). what is the speed of a 14 kN body at rest then falling from a height of 238 m. 2). How much…

A: Click to see the answer

Q: 1)Establish the difference between kinetic energy and gravitational potential energy with example.

A: We have to Establish the difference between kinetic energy and gravitational potential energy with…

Q: A 71.6-kg boy is surfing and catches a wave which gives him an initial speed of 1.60 m/s. He then…

A: Click to see the answer

Q: (1) A chimp climbs on to a wall that is 3.6m high and gains 2 268 J of potential energy. What is the…

A: Click to see the answer

Q: 4. A 50 gram golf ball is shot from the top of a cliff at a speed of 20.0 m/s. The ball lands on the…

A: Click to see the answer

Q: A new ride being built at an amusement park includes a vertical drop of 71.6 meters. Starting from…

A: Click to see the answer

Q: A new ride being built at an amusement park includes a vertical drop of 71.6 meters. Starting from…

A: The potential energy of the cart-passengers system can be calculated as,

Q: A 68.2-kg boy is surfing and catches a wave which gives him an initial speed of 1.60 m/s. He then…

A: Given; m=68 kgu=1.6 m/s h=1.64 mv=8.5 m/s It is required to calculate the non conservative work…

Q: A 68.2-kg boy is surfing and catches a wave which gives him an initial speed of 1.60 m/s. He then…

A: Click to see the answer

Q: If you run down some stairs and stop, what happens to your kinetic energy and your initial…

A: In the absence of dissipative forces, the total mechanical energy of closed system remains…

Q: If you run down some stairs and stop, what happens to your kinetic energy and your initial…

A: Run down on the stairs and then stop

Q: At what rate is a 58.64-kg boy using energy when he runs up a flight of stairs 9.37-m high, in 6.79…

A: mass of boy (m) = 58.64 kg height of stairs (h) = 9.37 m time taken (t) = 6.79 seconds

Q: Your brain consumes about 22 W of power,and avocados have been shown to promote brain health. If…

A: Given data: Power consumed by the brain is, P = 22 W Each avocado contains the energy of, E = 310…

Q: To combat wasteful habits, we often speak of “conserving energy,” by which we mean turning off…

A: Click to see the answer

Q: 5. A 50 kg log is floating above a waterfalls at a rate of 10 m/s, What will be the resulting…

A: Given: Mass of the log, M=50Kg The velocity of a floating log, vi=10 m/s The velocity of log falls…

Q: 1. A student of mass 40 kg caries a bag weighing 5000g from the ground floor to his class on the…

A: Since all the questions are different, as per Bartleby guidelines only 1st one can be answered at a…

Q: Example 5.2 "Compare the energy required to travel 20 km on a bicycle to that needed by an auto for…

A: Write the given values of this problem. distance=20 kmρ=680 kg/m3Energy of gasoline=11.4 kcal/g or…

Q: 1.) A 75 kg sprinter accelerates from 0 to 8.0 m/s in 5.0 s. What is the output erergy, in kJ…

A: Click to see the answer

Q: While running, a person dissipates about 0.600 J of chemical energy to mechanical energy per step…

A: Click to see the answer

Q: If you want to jump as high as possible, it’s best to move downward quickly to a deep crouch,…

A: Crouch position is a position which is taken by an sprinter before sprinting off. As, it provide…

Q: In terms of saving energy, bicycling and walking arefar more efficient means of transportation than…

A: (a). The energy consumption by the person in walking is

Q: Assume running consumes 108 Calories per mile. If you run 9 minute miles, what is your average power…

A: givenwork done=108 calTime =9 min=960 hr

Q: A student eats a dinner rated at 2 000 Calories. He wishes to do an equivalent amount of work in the…

A: Click to see the answer

Q: In a bicycle race, a rider such as Lance Armstrong (mass = 70 kg) uses energy at a rate of 6.0 W/kg…

A: Click to see the answer

Q: 1- An 18,000g object is accelerated at 2m / s', if the object is displaced 40m. What is the work…

A: Click to see the answer

Q: Deep in the forest, a 17.0-g leaf falls from a tree and drops straight to the ground. If its initial…

A: In this case, initially, the leaf has gravitational potential energy, but no kinetic energy.   When…

Q: A 68 kg hiker walks at 5.0 km/h up a 7% slope. What is the necessary metabolic power?

A: Click to see the answer

Q: A 65-kg hiker climbs to the top of a mountain 4200 m high. The climb is made in 4.6 h starting at an…

A: Click to see the answer

Q: 5 - Which of the following regarding mechanical energy is absolutely correct? A) Always protected…

A: Mechanical energy: The mechanical energy  of any system is the sum of kinetic and potential energies…

Q: A woman lifts a single shopping bag weighing 100N from the ground to a height of 15cm. She then…

A: Solution: Given that weight = 100 N distance d = 2km = 2000 m height = h = 15 cm = 0.15 m

Q: A 900 N crate slides 12 m down a ramp that makes an angle of 35° with the horizontal. If the crate…

A: mg=Weight of crate=900 Nθ=Angle of slope=35°Length of ramp=12 m

Q: A bicyclist on a flat road expends energy at a rate of 80 W. How many Joules of energy are expended…

A: Click to see the answer

Q: 200-g block is pressed against a spring of force constant 1.40 kN/m until the block compresses the…

A: Click to see the answer

Q: Alice, whose mass is 55 kg, eats a jelly doughnut for breakfast. According to the nutrition label,…

A: The energy possessed by an object when it is raised to an height h above the ground is known as the…

Q: Suppose that the average U.S. household uses 14100 kWh (kilowatt-hours) of energy in a year. If the…

A: Click to see the answer

Q: A young couple realized that they overate by 1050 Calories each. To compensate they wanted to…

A: Click to see the answer

Knowledge Booster
Recommended textbooks for you
  • College Physics
    Physics
    ISBN:9781305952300
    Author:Raymond A. Serway, Chris Vuille
    Publisher:Cengage Learning
    University Physics (14th Edition)
    Physics
    ISBN:9780133969290
    Author:Hugh D. Young, Roger A. Freedman
    Publisher:PEARSON
    Introduction To Quantum Mechanics
    Physics
    ISBN:9781107189638
    Author:Griffiths, David J., Schroeter, Darrell F.
    Publisher:Cambridge University Press
  • Physics for Scientists and Engineers
    Physics
    ISBN:9781337553278
    Author:Raymond A. Serway, John W. Jewett
    Publisher:Cengage Learning
    Lecture- Tutorials for Introductory Astronomy
    Physics
    ISBN:9780321820464
    Author:Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina Brissenden
    Publisher:Addison-Wesley
    College Physics: A Strategic Approach (4th Editio...
    Physics
    ISBN:9780134609034
    Author:Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
    Publisher:PEARSON
  • College Physics
    Physics
    ISBN:9781305952300
    Author:Raymond A. Serway, Chris Vuille
    Publisher:Cengage Learning
    University Physics (14th Edition)
    Physics
    ISBN:9780133969290
    Author:Hugh D. Young, Roger A. Freedman
    Publisher:PEARSON
    Introduction To Quantum Mechanics
    Physics
    ISBN:9781107189638
    Author:Griffiths, David J., Schroeter, Darrell F.
    Publisher:Cambridge University Press
    Physics for Scientists and Engineers
    Physics
    ISBN:9781337553278
    Author:Raymond A. Serway, John W. Jewett
    Publisher:Cengage Learning
    Lecture- Tutorials for Introductory Astronomy
    Physics
    ISBN:9780321820464
    Author:Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina Brissenden
    Publisher:Addison-Wesley
    College Physics: A Strategic Approach (4th Editio...
    Physics
    ISBN:9780134609034
    Author:Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
    Publisher:PEARSON