Energy requirements of the body. A 70 kg human uses energy at the rate of 80 J/s, on average, for just resting and sleeping. When the person is engaged in more strenuous activities, the rate can be much higher. (a) If the individual did nothing but rest, how many food calories per day would she or he have to eat to make up for those used up? (b) In what forms is energy used when a person is resting or sleeping? In other words, what happens to those 80 J/s? (Hint: What kinds of energy, mechanical and otherwise, do our body components have?) (c) If an average person rested and did other low-level activity for 16 hours (which consumes 80 J/s) and did light activity on the job for 8 hours (which consumes 200 J/s), how many calories would she or he have to consume per day to make up for the energy used up?
Energy requirements of the body. A 70 kg human uses energy at the rate of 80 J/s, on average, for just resting and sleeping. When the person is engaged in more strenuous activities, the rate can be much higher. (a) If the individual did nothing but rest, how many food calories per day would she or he have to eat to make up for those used up? (b) In what forms is energy used when a person is resting or sleeping? In other words, what happens to those 80 J/s? (Hint: What kinds of energy, mechanical and otherwise, do our body components have?) (c) If an average person rested and did other low-level activity for 16 hours (which consumes 80 J/s) and did light activity on the job for 8 hours (which consumes 200 J/s), how many calories would she or he have to consume per day to make up for the energy used up?
Energy requirements of the body. A 70 kg human uses energy at the rate of 80 J/s, on average, for just resting and sleeping. When the person is engaged in more strenuous activities, the rate can be much higher. (a) If the individual did nothing but rest, how many food calories per day would she or he have to eat to make up for those used up? (b) In what forms is energy used when a person is resting or sleeping? In other words, what happens to those 80 J/s? (Hint: What kinds of energy, mechanical and otherwise, do our body components have?) (c) If an average person rested and did other low-level activity for 16 hours (which consumes 80 J/s) and did light activity on the job for 8 hours (which consumes 200 J/s), how many calories would she or he have to consume per day to make up for the energy used up?
43. A mass må undergoes circular
motion of radius R on a hori-
zontal frictionless table, con-
nected by a massless string
through a hole in the table to
a second mass m² (Fig. 5.33).
If m₂ is stationary, find expres-
sions for (a) the string tension
and (b) the period of the circu-
lar motion.
m2
R
m₁
FIGURE 5.33 Problem 43
CH
70. A block is projected up an incline at angle 0. It returns to its initial
position with half its initial speed. Show that the coefficient of ki-
netic friction is μk = tano.
Passage Problems
A spiral is an ice-skating position in which the skater glides on one
foot with the other foot held above hip level. It's a required element
in women's singles figure-skating competition and is related to the
arabesque performed in ballet. Figure 5.40 shows Canadian skater
Kaetlyn Osmond executing a spiral during her medal-winning perfor-
mance at the 2018 Winter Olympics in Gangneung, South Korea.
77. From the photo, you can conclude
that the skater is
a. executing a turn to her left.
b. executing a turn to her right.
c. moving in a straight line out of
the page.
78. The net force on the skater
a. points to her left.
b. points to her right.
c. is zero.
79. If the skater were to execute the same
maneuver but at higher speed, the tilt
evident in the photo would be
a. less.
b. greater.
c. unchanged.
FIGURE 5.40 Passage
Problems 77-80
80. The tilt angle 0 that the skater's body
makes with the vertical is given ap-
proximately by 0 = tan¯¹(0.5). From this you can conclude…
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.