(a) How many hours does it take him to work off a 450 Calorie bagel if he stays in bed all day?
(b) How long does it take him if he's working out?
2 h
(c) Calculate the amount of mechanical work necessary to lift a 126 kg barbell 2.10 m.
3 J
(d) He drops the barbell to the floor and lifts it repeatedly. How many times per minute must he repeat this process to do an amount of mechanical work equivalent to his metabolic rate increase of 650 W during exercise?
(a) To calculate how many hours it takes to work off a 450 Calorie bagel if he stays in bed all day, we need to know the number of Calories burned per hour while being inactive. Once we have that information, we can divide the total number of Calories in the bagel (450) by the Calories burned per hour to find the number of hours it takes.
(b) To calculate the amount of time it takes him to work off the bagel if he's working out, we need to know the number of Calories burned per hour during exercise. Once we have that information, we can divide the total number of Calories in the bagel (450) by the Calories burned per hour during exercise to find the number of hours it takes.
(c) To calculate the amount of mechanical work necessary to lift a 126 kg barbell 2.10 m, we can use the equation W = mgh, where W is the work done, m is the mass, g is the acceleration due to gravity, and h is the height. Plugging in the values, we can calculate the work done.
(d) To calculate the number of times per minute he must repeat lifting the barbell to do an amount of mechanical work equivalent to his metabolic rate increase of 650 W during exercise, we need to know the amount of work done per repetition. Once we have that information, we can divide the total work done (650 W) by the work done per repetition to find the number of repetitions per minute.