18. The energy value of food is determined by burning a sample of
the food and measuring the heat
released. The energy rating
assigned to the food is actually a
kilocalorie (1000 calories), written
as a Calorie (with a capital C).
Thus,
1 Calorie = 1 kilocalorie.
(a) The nutrition facts for a
popular brand of cookimare
shown at the right. How many
Calories are in one of these
cookies?
(b) How many calories of heat
would be released from
burning one of the cookies?

You are still fascinated by the process of inkjet printing, as described in the opening storyline for this chapter. you convince your father to take you to his manufacturing facility to see the machines that print expiration dates on eggs. you strike up a conversation with the technician operating the machine. he tells you that the ink drops are created using a piezoelectric crystal, acoustic waves, and the plateau-rayleigh instability, which creates uniform drops of mass m = 1.25 ✕ 10−8 g. while you don't understand the fancy words, you do recognize mass! the technician also tells you that the drops are charged to a controllable value of q and then projected vertically downward between parallel deflecting plates at a constant terminal speed of 20.0 m/s. the plates are ℓ = 2.15 cm long and have a uniform electric field of magnitude e = 6.40 ✕ 104 n/c between them. noting your interest in the process, the technician asks you, "if the position on the egg at which the drop is to be deposited requires that its deflection at the bottom end of the plates be 0.17 mm, what is the required charge on the drop (in c)? " you quickly get to work to find the answer. (neglect the force of gravity.)