Which of the following polymer combinations is least likely to mix?
(a) Liquids of two different long-chain molecules with a positive enthalpy of mixing.
(b) A liquid solvent and solid polymer with solubility parameters of 19 MPa0.5 and 20 MPa0.5, respectively.
(c) Liquids of two different long-chain molecules with a negative enthalpy of mixing.
(d) Liquids of two different short molecules with a positive enthalpy of mixing.
(a) Liquids of two different long-chain molecules with a positive enthalpy of mixing.
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An object is attached to a vertical spring and bobs up and down between points A and B. Where is the object located when the elastic potential energy of the system object-spring is a minimum?
A) at either A or B B) midway between A and B C) one-third of the way between A and B D) one-fourth of the way between A and B E) at none of the above points
Rocks begin to deform when they are stressed. Near Earth's surface, when stress is severe, the rock
A) behaves plastically—it folds and flows. B) Is brittle—it breaks producing faults and fractures. C) has brittle deformation—it folds and flows. D) has plastic deformation—it faults and fractures.
All planetary nebulae are slowly-expanding spherical disks ejected by red giants, while their exposed cores appear as white dwarfs
Indicate whether the statement is true or false
An astronaut has landed on an asteroid and conducts an experiment to determine the acceleration of gravity on that asteroid. She uses a pendulum that has a period of oscillation of 2.00 s on Earth and finds that on the asteroid the period is 11.3 s
What is the acceleration of gravity on that asteroid? A) 0.307 m/s2 B) 1.66 m/s2 C) 1.74 m/s2 D) 5.51 m/s2 E) 0.0544 m/s2