Physics, 26.07.2019 17:00 ayoismeisjjjjuan

Rob is attempting to dissolve rock salt in warm water but it is a slow process. how could he most effectively increase the rate of solution of the rock salt? a) decrease the temperature of the water. b) increase the concentration of the salt. c) grind the rock salt into smaller pieces. d) agitate the rock salt and the cool water.

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Answer from: yofavkay

C) Grind the rock salt into smaller pieces.

Explanation:

To dissolve rock salt we need certain amount of heat, which is provided by the warm water. Now, this warm water won't dissolve easily the rock salt, because that salt in that state as rock, it's harder, that is, the heat won't penetrate easily in to the material to dissolve it.

Now, if we grind the rock salt into smaller pieces, we'll accelerate the process, because each pieces requires less heat to be dissolved. Basically, when we do smaller pieces, we are giving the energy needed to grind that rock, and such energy won't be needed from the warm water, so the actual energy from the warm water will be focused on dissolving each small piece.

Therefore, the right answer is C.

Answer from: Quest

a straight line sloped

Answer from: Quest

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

$x(t)=ax(x-6)$

where $a$ is unknown. because the position is parabolic, there is symmetry about the midpoint at $t=3$ , and we know that

$x(3)=10\implies -9a=10\implies a=-\dfrac{10}9$

so that the position function is

$x(t)=-\dfrac{10}9x(x-6)$

which means the velocity is

$v(t)=\dfrac{\mathrm dx}{\mathrm dt}=-\dfrac{20}9x+\dfrac{60}9$

then the total distance traveled is

$\displaystyle\int_{t=0}^{t=6}|v(t)|\,\mathrm dt=\left\{\int_{t-0}^{t=3}-\int_{t=3}^{t=6}\right\}v(t)\,\mathrm dt=20$

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at $x=0$ and ends at $x=0$ , so its displacement is 0.

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Rob is attempting to dissolve rock salt in warm water but it is a slow process. how could he most ef...

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