Answer:
its durable. it's cheap. its recyclable
Explanation:
Plastic is made of lots of recycled materials that make it very useful and cheap.
An engineer must design a rectangular box that has a volume of 9 m3 and that has a bottom whose length is twice its width. What are the dimensions of the box so that the total surface area (of all six sides) of the box is minimized
Answer:
[tex]Length =3[/tex] [tex]Height = 2[/tex] and [tex]Width = \frac{3}{2}[/tex]
Explanation:
Given
[tex]Volume = 9m^3[/tex]
Represent the height as h, the length as l and the width as w.
From the question:
[tex]Length = 2 * Width[/tex]
[tex]l = 2w[/tex]
Volume of a box is calculated as:
[tex]V = l*w*h[/tex]
This gives:
[tex]V = 2w *w*h[/tex]
[tex]V = 2w^2h[/tex]
Substitute 9 for V
[tex]9 = 2w^2h[/tex]
Make h the subject:
[tex]h = \frac{9}{2w^2}[/tex]
The surface area is calculated as:
[tex]A = 2(lw + lh + hw)[/tex]
Recall that: [tex]l = 2w[/tex]
[tex]A = 2(2w*w + 2w*h + hw)[/tex]
[tex]A = 2(2w^2 + 2wh + hw)[/tex]
[tex]A = 2(2w^2 + 3wh)[/tex]
[tex]A = 4w^2 + 6wh[/tex]
Recall that: [tex]h = \frac{9}{2w^2}[/tex]
So:
[tex]A = 4w^2 + 6w * \frac{9}{2w^2}[/tex]
[tex]A = 4w^2 + 6* \frac{9}{2w}[/tex]
[tex]A = 4w^2 + \frac{6* 9}{2w}[/tex]
[tex]A = 4w^2 + \frac{3* 9}{w}[/tex]
[tex]A = 4w^2 + \frac{27}{w}[/tex]
To minimize the surface area, we have to differentiate with respect to w
[tex]A' = 8w - 27w^{-2}[/tex]
Set A' to 0
[tex]0 = 8w - 27w^{-2}[/tex]
Add [tex]27w^{-2}[/tex] to both sides
[tex]27w^{-2} = 8w[/tex]
Multiply both sides by [tex]w^2[/tex]
[tex]27w^{-2}*w^2 = 8w*w^2[/tex]
[tex]27 = 8w^3[/tex]
Make [tex]w^3[/tex] the subject
[tex]w^3 = \frac{27}{8}[/tex]
Solve for w
[tex]w = \sqrt[3]{\frac{27}{8}}[/tex]
[tex]w = \frac{3}{2}[/tex]
Recall that : [tex]h = \frac{9}{2w^2}[/tex] and [tex]l = 2w[/tex]
[tex]h = \frac{9}{2 * \frac{3}{2}^2}[/tex]
[tex]h = \frac{9}{2 * \frac{9}{4}}[/tex]
[tex]h = \frac{9}{\frac{9}{2}}[/tex]
[tex]h = 9/\frac{9}{2}[/tex]
[tex]h = 9*\frac{2}{9}[/tex]
[tex]h= 2[/tex]
[tex]l = 2w[/tex]
[tex]l = 2 * \frac{3}{2}[/tex]
[tex]l = 3[/tex]
Hence, the dimension that minimizes the surface area is:
[tex]Length =3[/tex] [tex]Height = 2[/tex] and [tex]Width = \frac{3}{2}[/tex]
If most wildfires are suppressed (all fires are put out) for many years, how does the risk of wildfire in the area change in the future?
There will be a higher risk of wildfires
There will be a lower risk of wildfires
There is no difference in risk
Explain your answer.
Answer:
there is no difference in risk
Explanation:
even though they put out the fires, if they don't get rid of the source from which the wildfires comes from then wildfires wont stop coming
The purpose of pasteurizing milk is to
A. Kill pathogens
B. Break down milk fat
C. Add vitamins and minerals
D. Prevent spoilage by sunlight
Plis can someone help me ?
Answer:
i think it c
Explanation:
Compute the weight fraction of graphite, in a 3 wt% C Ferritic Gray cast iron, assuming that all the carbon exists as the graphite phase. Assume densities of 7.9 and 2.3 g/cm3 for ferrite and graphite, respectively.
Answer:
9.60%
Explanation:
Computation for the weight fraction of graphite
First step
Computation for the mass fraction for Wa using this formula
Wa=Cg-Co/Cg-Ca
Let plug
Wa=10-3/100-0
Wa=0.97
Computation for the mass fraction for Wg using this formula
Wg=Co-Ca/Cg-Ca
Let plug in the formula
Wg=3-0/100-0
Wg=0.03
Second step is to convert the mass fraction to Volume Fraction using this formula
Volume Fraction =[Wg/Pg÷(Wa/Pa)+(Wg/Pg)]*100
Let plug in the formula
Volume =[0.03/2.3 ÷(0.97/7.9)+(0.03/2.3)]*100
Volume=[0.0130435÷0.1227848+0.0130435]*100
Volume=[0.0130435÷0.135828]*100
Volume=0.096*100
Volume=9.60%
Therefore the weight fraction of graphite will be 9.60%
A piece of corroded steel plate was found in submerged ocean vessel. It was estimated that the area of plate to be ~38 inch 2, and weight loss due to corrosion was 1.9 Kg. Assuming a corrosion rate of 120 mpy for this steel in seawater, estimate the of submersion time in years for this steel plate?
Answer:
3.2 years
Explanation:
The corrosion penetration rate (CPR) is given by:
[tex]CPR=\frac{KW}{\rho At} \\\\Where:\\K=constant, W=weight\ loss, \rho=density\ of\ specimen, A=area\ of\ exposed\ specimen, t=time\ exposed[/tex]
Given that:
CPR = 120 mpy, W = 1.9 kg = 1900 g, density of steel = 7.9 g/cm³, A = 38 in², K = 534 (for 10⁻³ in per year),
Substituting:
[tex]120 \ mpy=\frac{534*1900\ g*(10^3\ mg/g)}{7.9g/cm^3*38\ in^2*t} \\\\t=\frac{534*1900\ g*(10^3\ mg/g)}{7.9g/cm^3*38\ in^2*120\ mpy} \\\\t= 28164.56\ hours\\\\t=\frac{28164.56\ hours}{24\ hr/day*365\ day/year}\\\\t= 3.2 \ years[/tex]
Design an integral controller for the plant to yield a step response with 10% overshoot, a peak time of 2 seconds, and zero steady-state error.
Answer:
is this an essay if so you need to have stop response that is 10% in the overshoot and put it in 2 seconds
Explanation:
What must be used in series with a forward- biased diode to prevent damage due to excessive 15) current
Answer:
A resistor
Explanation:
A diode is an electrical device that allows current to pass through it only in one direction. When a diode is forward biased, it allows current to flow through it in direction but when it is reverse biased, it stops current from flowing through it.
The maximum forward current is the maximum current allowed to flow through the diode when conducting in the forward bias condition. If the maximum forward current is exceeded, it leads to heat which causes damage to the diode.
A resistor is conducted in series to the forward biased diode to limit the current flowing through it thereby ensuring that the current is below the maximum forward current.
4. The process of heating milk to kill microorganisms that cause spoilage and disease without affecting its nutritional value is called
A. Homogenization
B. Pasteurization
C. Boiling
D. Poaching
Answer:
I think the answer is C. Boiling but I'm not 100% sure.
The thermodynamic property used to determine the amount of work produced by a power turbine in a heat engine is:_______
Answer:
Enthalpy
Explanation:
Thermodynamic properties could be Intensive or extensive properties. Intensive properties are those that don't depend on the quantity of matter. Examples are pressure & temperature. Meanwhile, extensive properties are those whose values depend on the mass of the system. Examples are Energy, enthalpy and volume.
Now, in turbines in thermodynamics, the work done is produced by the flow required to turn the turbine and shaft. Recall that from the law of conservation of energy, the work in the turbine per mass airflow would be equal to the change in specific enthalpy of the flow from the entrance to the exit point of the turbine.
Thus, the property required to determine the work is Enthalpy.
Which of the following types of equipment are run by an operation in a rotating cab?
Answer:
Motor Vehicles, Mechanized Equipment, and Marine Operations ... These rules apply to the following types of earthmoving equipment: scrapers, loaders, ... which shall be operated as needed when the machine is moving in either direction
The purpose of pasteurizing milk is to A. Kill pathogens B. Break down milk fat C. Add vitamins and minerals D. Prevent spoilage by sunlight
How many flip-flop values are complemented in an 8-bit binary ripple counter to reach the next count value after: 0110111 and 01010110?
Answer:
- Four (4) flip-flop values will complemented
- one (1) flip-flop value will complemented
Explanation:
To find how many flip flop number of bits complemented, we just need to figure out what the next count in the sequence is and find how many bits have changed.
taking a look at the a) 00110111
we need to just 1 to the value,
so
00110111 + 0000001 = 00111000
So here, only the first four bits are complemented.
Therefore Four (4) flip-flop values will complemented
Next
b) 01010110
we also add 1 to the value
01010110 + 00000001 = 01010111
only the first bit is complemented.
Therefore one (1) flip-flop value will complemented
A system will never enter a deadlocked state if:__________A) the system chooses to ignore the problem altogether.B) the system uses the detection and recovery technique.C) the system uses the deadlock avoidance technique.D) None of the above.
A system will never enter a deadlocked state if the system uses the detection and recovery technique. Thus the correct option is B.
What is deadlocked state?A deadlock in desktop software happens when a procedure or task enters a waiting state as a result of another waiting process holding the requested system resource.
When a group of processes is in a wait state, a deadlock occurs because each process is awaiting a resource that is being held by another waiting process.
The wait-for graph must be maintained by the system in order to detect deadlocks, and the system periodically runs an operation that looks for cycles in the wait-for graph.
There is no method used by the OS to avoid or stop deadlocks. The OS checks the system on a regular basis for any deadlocks in an effort to break them. Therefore, option B is appropriate.
Learn more about the detection and recovery technique, here:
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