A 120-pound woman working in an office expends about 2.2 3 103 kcal/day,whereas the same woman climbing a mountain needs 3.4 3 103 kcal/day. (a) How many joules per day does the woman expend in each activity? (b) How many seconds are in 1 day? (c) How many joules per second (5 watts) does the woman expend in each activity? (d) Which consumes more power (watts), the office worker or a 100-W light bulb?

A 120-pound woman working in an office expends about 2.2 3 103 kcal/day,whereas the same woman climbing a mountain needs 3.4 3 103 kcal/day. (a) How many joules per day does the woman expend in each activity? (b) How many seconds are in 1 day? (c) How many joules per second (5 watts) does the woman expend in each activity? (d) Which consumes more power (watts), the office worker or a 100-W light bulb?

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter17: Energy In Thermal Processes: The First Law Of Thermodynamics

Section: Chapter Questions

Problem 61P

See similar textbooks

Similar questions

Sewage at a certain pumping station is raised vertically by 5.49 m at the rate of 1 890 000 liters each day. The sewage, of density 1 050 kg/m3, enters and leaves the pump at atmospheric pressure and through pipes of equal diameter. (a) Find the output mechanical power of the lift station. (b) Assume an electric motor continuously operating with average power 5.90 kW runs the pump. Find its efficiency.
Energy is conventionally measured in Calories as well as in joules. One Calorie in nutrition is 1 kilocalorie, which we define in Chapter 11 as 1 kcal = 4 186 J. Metabolizing 1 gram of fat can release 9.00 kcal. A student decides to try to lose weight by exercising. She plans to run up and down the stairs in a football stadium as fast as she can and as many times as necessary. Is this in itself a practical way to lose weight? To evaluate the program, suppose she runs up a flight of 80 steps, each 0.150 m high, in 65.0 s. For simplicity, ignore the energy she uses in coming down (which is small). Assume that a typical efficiency for human muscles is 20.0%. This means that when your body converts 100 J from metabolizing fat, 20 J goes into doing mechanical work (here, climbing stairs). The remainder goes into internal energy. Assume the students mass is 50.0 kg. (a) How many times must she run the flight of stairs to lose 1 pound of fat? (b) What is her average power output, in watts and in horsepower, as she is running up the stairs?
A 50.0-kg student evaluates a weight loss program by calculating the number of times she would need to climb a 12.0-m high flight of steps in order to lose one pound (0.45 kg) of fat. Metabolizing 1.00 kg of fat can release 3.77 107 J of chemical energy and the body can convert about 20.0% of this into mechanical energy. (The rest goes into internal energy.) (a) How much mechanical energy can the body produce from 0.450 kg of fat? (b) How many trips up the flight of steps are required for the student to lose 0.450 kg of fat? Ignore the relatively small amount of energy required to return down the stairs.
From the table below which shows the metabolic rate for each activity, if a person with height 1.50m and weight of 60kg completed all these activities in one day. Calculate the person's one day energy expenditure. Activity8hr sleeping (35 Cal/m^2 -hr)8hr moderate physical labor (150 Cal/m^2 -hr)4hr reading, writing, TV watching (60 Cal/m^2 -hr)1hr heavy exercise (300 Cal/m^2 -hr)1hr dressing, eating (100 Cal/m^2 -hr)
If a typical city consumes electrical energy at a rate of 2.0 GW (that's 2 billion joules per second), how many kilograms of matter would have to be converted entirely into electrical energy in order to keep this city running for 14 weeks? (c = 3.0 × 108 m/s)
A sleeping 68 kg man has a metabolic power of 75 W . How many Calories does he burn during an 8.0 hour sleep? Express your answer using two significant figures.
How much work is done in blowing up a balloon from zero volume to a volume of 6.4 L, assuming that p = 1.00 bar and no work is required to stretch the rubber? (In reality, the work that goes into stretching the rubber is substantial.)
An “energy bar” contains 22 g of carbohydrates. If the energy bar was his only fuel, how far could a 68 kg person walk at 5.0 km/h?
A 68-kg woman is planning to bicycle for an hour. If she is to meet her entire energy needs while bicycling by eating 30-g chocolate candy bars, determine how many candy bars she needs to take with her.
A typical avocado has 180 Calories. If all this energy could be used to lift a bucket of water weighing 40 N, through what vertical distance could the bucket be lifted? (1 calorie = 4.184 J and 1 Calorie = 103 calories) a. 1.72E+6 m b. 3.01E+7 m c. 7.53E+5 m d. 1.88E+4 m
Energy that is not utilized for work or heat transfer in the human body is converted to the chemical energy of body fat, which contains about 39 kJ/g. How many grams of fat will you gain if you eat 2450 kcal one day and do nothing but sit relaxed for 16 hours and sleep for the other 8 hours. (Assume sleeping burns 1.2 kcal/min, while sitting relaxed burns 1.7 kcal.min)
A 53−kg person drinks5.4×102g of milk, which has a caloric value of approximately 3.0 kJ/g.If only 17 percent of the energy in milk is converted to mechanical work, how high (in meters) can the person climb based on this energy intake? Enter your answer in scientific notation. Hint: The work done in ascending is given by mgh, where m is the mass (in kg), g is the gravitational acceleration(9.8 m/s2), and h is the height (in meters).