Which portion of the electromagnetic spectrum is used to sterilize medical instruments?
a. infrared waves
b. microwaves
c. X rays
d. ultraviolet light
Ans: d. ultraviolet light
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DNA is important to a cell because
a. DNA is the cell membrane that allows nutrients to enter the cell and waste to leave. b. DNA contains the information necessary to make all of the molecules required by the organism. c. DNA contains the information necessary for the cell to reproduce itself. d. all of the above e. b and c above
Water flowing through a pipe is heated by steam condensing on the outside of the pipe. (a) Assuming a uniform overall heat transfer coefficient along the pipe, derive an expression for the water temperature as a function of distance from the entrance. (b) For an overall heat transfer coefficient of 570 W/(m2 K), based on the inside diameter of 5 cm, a steam temperature of 104°C, and water-flow rate of 0.063 kg/s, calculate the length required to raise the water temperature from 15.5 to 65.5°C.
GIVEN
• Water flowing through a pipe steam condensing on the outside
FIND
(a) An expression for the water temperature as a function of distance from the entrance, Tw (x)
(b) For Overall heat transfer coefficient (U) = 570 W/(m2 K)
Inside diameter (D) = 5 cm = 0.05 m
Steam temperature (Ts) = 104°C
Water flow rate ( m w) = 0.063 kg/s
Water temperatures: Tw,in = 15.5°C Tw,out = 65.5°C
Find the length (L) required
ASSUMPTIONS
• A uniform overall heat transfer coefficient
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of water at the mean temperature of 40°C (cpw) =4175 J/(kg K)
An electron and a proton are each released from rest in the same uniform electric field. The electron moves a distance delectron and the proton moves a distance dproton as each particle's kinetic energy increases by 1.6 eV. How do delectron and dproton compare?
a. delectron < dproton b. delectron > dproton c. delectron = dproton d. The answer depends on the direction of the electric field.
Molten rock material on Earth's surface is known as ______________
Fill in the blank(s) with correct word