Which best describes convection

Physics

2 answers:

Dmitriy789 [7]3 years ago

7 0

It is driven by tempature differences within the fluid

Inessa [10]3 years ago

4 0

Correct answer: transfer of heat by the actual movement of warmed matter. Because warm air rises and cooler air falls due to density differences. My son just took this quiz.

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Highway safety engineers build soft barriers so that cars hitting them will slow down at a safe rate. a person wearing a safety

matrenka [14]

Basically, we want to see the distance in terms of thickness. So, for this rectilinear motion at constant acceleration, the equation to be used is:

x = v₀t + 0.5at²

First, let's determine t using the equation:
a = |v - v₀|/t
300 m/s² = |0 - 92.8 km/h * 1,000 m/1 km * 1 h/3600 s|/t
t = 0.086 seconds

x = (92.8 km/h * 1,000 m/1 km * 1 h/3600 s)(0.086 s) + 0.5(300 m/s²)(0.086 s)²
x = 3.33 meters

5 0

2 years ago

A rectangular metal tank with an open top is to hold 171.5 cubic feet of liquid. what are the dimensions of the tank that requir

Semmy [17]

To minimize the material usage we have to have the volume requested with the minimum surface area.
The volume is:
$171.5 =xyz$
And the surface is:
$S=xy+2xz+2yz$
From the first equation we get:
$z=\frac{171.5}{xy} ; k=171.5\\ z=\frac{k}{xy}\\$
I will use k instead of a number just for the conveince.
We plug this into the second equation and we get:
$S=xy+2k\frac{1}{x}+2k\frac{1}{y}$
To find the minimum of this function we have to find the zeros of its first derivative.
Sx will denote the first derivative with respect to x and Sy will denote the first derivative with respect to Sy.
$S_x=y-2k\frac{1}{x^2}\\ S_y=x-2k\frac{1}{y^2}$
Now let both derivatives go to zero and solve the system (this will give us the so-called critical points).
$0=y-2k\frac{1}{x^2}\\
0=x-2k\frac{1}{y^2}\\
y=2k\frac{1}{x^2}\\
x=2k\frac{1}{y^2}\\$
Now we plug in the first equation into the other and we get:
$x=\frac{\frac{2k}{1}}{\frac{4k^2}{x^4}}\\
x^3=2k\\
x=(2\cdot171.5)^{1/3}\\
x=7
$
Now we can calculate y:
$y=2k\frac{1}{x^2}\\
y=2\cdot 171.5\frac{1}{7^2}=7$
And finaly we calculate z:
$z=\frac{171.5}{xy}\\
z=\frac{171.5}{7\cdot7}=3.5$
And finaly let's check our result:
$V=xyz=7\cdot7\cdot3.5=171.5$

4 0

2 years ago

Please help me i dont get it

Dima020 [189]

The answers are:

39:

a - 1 mile

b - 0 miles

40:

$a=-4\frac{m}{s^{2} }$

41:

$Displacement=3.60 miles\\Distance=5 miles$

Why?

Solving 39:

To answer the questions, we need to remember that distance and displacement are different things. Distance refers to the total "ground" covered during motion, while displacement refers to how far is the object/body from its starting point.

So,

39:

a - the total distance traveled corresponds to the length of the track which is 1 mile.

b - The displacement is equal to 0 because they finished at the starting point, the distance between the starting and the finishing point is equal to 0.

40:

We can solve the problem using one of the given equations:

$a=\frac{v_f-v_i}{t}$