Please help I’m about to fail
Answer:
B
Explanation:
The cost of manufacturing would have to be taken away from your profits becuase its costing you to build and get the materials. I believe this question is hard.
In a test of a new UV-curable polymeric material (with thermal conductivity 0.15 W/(m K)) for dental prostheses, a 2.8 mm thick slab is subjected to monochromatic light with wavelength 313 nm, which is absorbed by the polymeric material according to the Beer Lambert Law of exponential attenuation. The material's surface is exposed to light at z = 0 , the rate at which light is absorbed (with dimensions of photons per unit volume per unit time) is 0 z I e γ γ − , where 0 I is the incident photon flux (with dimensions of photons per unit area per unit time), and 4 1 γ 3 10 m− − = × . (This approximation neglects the temporal decrease in absorption, among other things.) We also assume that all absorbed radiation is converted to thermal energy. (This neglects thermochemical change in the material.) If the two surfaces of the polymeric material (at z = 0 and z = 2.8 mm ) are held at 38°C, what is the largest allowable value of 0 I so that, at steady state, the maximum temperature in the polymeric material does not exceed 44°C
Answer:
The largest allowable Io = 5.863 * 10^26 photons
Explanation:
thickness of slab = 2.8 mm
First we express the energy of each photon
[tex]E = \frac{hc}{wavelength}[/tex]
wavelength = 313 nm
attached below is the detailed solution on how i arrived at the answer above
note : we use 2 in the integral because the slab is exposed to light from two different direction
how many Kingdoms are there?
Answer:
5
Explanation:
Answer:
There are 5 kingdoms
Explanation:
The scheme most often used currently divides all living organisms into five kingdoms: Moneran (bacteria), Protista, Fungi, Plantae, and Animalia. This coexisted with a scheme dividing life into two main divisions: the Prokaryote (bacteria, etc.) and the Eukaryotae (animals, plants, fungi, and protists).
What are three ways people manipulate light.
Answer:
refracted, reflected, or absorbed.Explanation:
A car is travelling to the right with a speed of 42 m/s when the driver slams on the brakes the car skids 4.0 second
Answer:
84m
Explanation:
what do you understand by diffusion?
Answer:
Diffusion is a result of the kinetic properties of particles of matter. The particles will mix until they are evenly distributed. Diffusion may also be thought of as the movement of particles down a concentration gradient. The term "diffusion" comes from the Latin word diffundere, which means "to spread out."
Explanation:
A car travels in a straight line for 5 h at a constant speed of 72 km/h. What is it’s acceleration
Answer:
[tex] a \approx \: 0.001 \: m {s}^{ - 2} [/tex]
Explanation:
Given:
[tex]initial \: velocity \: (u) = 0 \\ \\
Final \: Velocity \: (v) = 72 km /h \\ \\
Time \: (t) = 5 \: hours \\ \\
Acceleration \: (a) =? \\ \\
\because \: a = \frac{v - u}{t} \\ \\ \therefore \: a = \frac{72 - 0}{5} \\ \\ a = \frac{72}{5} \\ \\ a = 14.5 \: km {h}^{ - 2} \\ \\ a = \frac{14.5 \times 1000}{3600\times 3600} \: m {s}^{ - 2} \\ \\ a = 0.00111882716 \\ \\ a \approx \: 0.001 \: m {s}^{ - 2} [/tex]
Bx = -1.33 m and By = 2.81 m.
Find the direction of the vector.
Answer:
Explanation:
The vector in unit vector notation is:
B = (-1.33m)i + (2.81m)j
To find the direction relative to the x-axis. Do inverse tangent of opposite/adjacent
[tex]tan^-^1=|\frac{2.81}{1.33}| = 2.11\\180-2.11=177.89[/tex]
This is relative to the positive x-axis
2.11 would be the correct answer if relative to the negative x axis
A student examines the effect of the number of D batteries in a closed circuit on the brightness of a light bulb. In the experiment, four circuits were built with 1, 2, 3, and 4 batteries respectively. For each trial, the brightness of the light bulb was measured using a light meter. Which variable should the student keep constant?
the type of batteries
the number of batteries
the brightness of the light bulb
the data collected from the light meter
The correct answer is the Type of batteries
Explanation:
In an experiment, it is normal the researcher modifies one variable, in this case, the number of batteries (independent variable), and this variable affects the variable tested, in this case, the brightness of the bulb (dependent variable).
However, other factors or variables should be constant to guarantee the results are reliable. In this context, one factor that the student should keep constant is the type of batteries he uses because this is not one of the main variables and therefore it is not expected he changes this on purpose or this is affected by other variables. Moreover, by making any change the experiment can be negatively affected. For example, batteries might differ in their power capacity this can affect the brightness of the bulbs.
The slope of a displacement position) vs time graph is a measurement called ____?
a) distance
b ) velocity
c ) speed
d) correlation
Answer:
velocity
Explanation:
velocity = displacement/ time
Two 11.5-mg balls are connected by a 28.9-cm-long insulating rod of negligible mass. One ball has a charge of +q and the other has a charge of −q. The system is placed in a 592 N/C uniform electric field. Initially the system is at rest and makes an angle α= 58.9° with respect to the field. It is then released, and when it is momentarily aligned with the electric field, its kinetic energy is 4.86 mJ. What is the magnitude of q?
Answer:
58.8 μC
Explanation:
The two balls create a dipole of dipole moment , p = qd where q = charge and d = distance between the charges = 28.9 cm = 0.289 m. The potential energy change ΔU = -W where W is the work done by the electric field of magnitude E = 592 N/C.
Now U = -pdEcosФ = -qdEcosФ where Ф is the angle between p and E. Since Ф is initially 58.9° and then becomes 0° when p and E align, the potential energy change is thus.
ΔU = -qdEcos0 - (-qdEcos58.9°) = qdE(cos58.9° - 1) = qdE(0.5165 - 1) = -0.4835qdE.
W = - ΔU = -(-0.4835qdE) = 0.4835qdE
This work equals the kinetic energy of the systems. Since K.E = 4.86 mJ = 4.86 × 10⁻³ J.
So K.E = W
K.E = 0.4835qdE
making q subject of the formula
q = K.E/0.4835dE
q = 4.86 × 10⁻³ J/(0.4835 × 0.289 m × 592 N/C)
q = 4.86 × 10⁻³ J/82.72
q = 0.0588 × 10⁻³ C
q = 58.8 × 10⁻⁶ C
q = 58.8 μC
When a certain air-filled parallel-plate capacitor is connected across a battery, it acquires a charge of 200 µC on each plate. While the battery connection is maintained, a dielectric slab is inserted into, and fills, the region between the plates. This results in the accumulation of an additional charge of 250 µC on each plate. What is the dielectric constant of the dielectric slab?
Answer:
The value is [tex]\epsilon = 2.25 [/tex]
Explanation:
From the question we are told that
The charge acquired on each plate is [tex]q = 200 \mu C = 200 *10^{-6} \ C[/tex]
The additional charge accumulated on each plate is [tex]q_a = 250 \mu C = 250 *10^{-6} \ C[/tex]
Generally the capacitance of the capacitor before a dielectric slab is inserted is
[tex]C_i = \frac{q}{V}[/tex]
=> [tex]C_i = \frac{200 \mu C}{V}[/tex]
Generally the total charge on each plate of the capacitor when the dielectric slab was inserted is
[tex]Q = q + q_a[/tex]
=> [tex]Q = ( 200 + 250 ) \mu C[/tex]
=> [tex]Q = 450 \mu C[/tex]
Generally the capacitance of the capacitor after a dielectric slab is inserted is mathematically represented as
[tex]C = \frac{450 \mu C}{V}[/tex]
Generally the dielectric constant is mathematically represented as
[tex]\epsilon = \frac{C}{C_i}[/tex]
=> [tex]\epsilon = \frac{450 \mu C}{200 \mu C}[/tex]
=> [tex]\epsilon = 2.25 [/tex]
The dielectric constant of the dielectric slab is 2.25.
Calculation of the dielectric constant:Since the charge on each playe should be q = 200 µC = 200*10^-6C
Now the additional charge accumulated should be
qa = 250µC = 250*10^-6C
Now we know that
Ci = q/v
Ci = 200µC/ V
Also,
Q = q+ qa
= 9200 + 250)µC
= 450µC
Now C = 450µC / V
So here the dielectric constant should be
= 450µC/200µC
= 2.25
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A.) If its booster rockets accelerate the space shuttle at 15m/s2, how high will it be one minute after launch?
B.) What was its average velocity
during that time?
Answer:
27,000 m
450 m/s
Explanation:
Assuming the initial velocity is 0 m/s:
v₀ = 0 m/s
a = 15 m/s²
t = 60 s
A) Find: Δy
Δy = v₀ t + ½ at²
Δy = (0 m/s) (60 s) + ½ (15 m/s²) (60 s)²
Δy = 27,000 m
B) Find: v_avg
v_avg = Δy / t
v_avg = 27,000 m / 60 s
v_avg = 450 m/s
3. A sample of argon of mass 6.56 g occupies 18.5 dm? at 305 K. (a) Calculate the work done when the gas expands isothermally against a constant external pressure of 7.7 kPa until its volume has increased by 2.5 dm'. (b) Calculate the work that would be done if the same expansion occurred reversibly.
Answer:
(a) [tex]W=-19.25J[/tex]
(b) [tex]W=-52.8J[/tex]
Explanation:
Hello.
(a) In this case, since the initial volume is 18.5 dm³ and the final volume is 21 dm³ (18.5 +2.5), we can compute the work at constant pressure as shown below:
[tex]W=-P\Delta V=-7.7kPa*\frac{1000Pa}{1kPa} (21dm^3-18.5dm^3)*\frac{1m^3}{1000dm^3}\\ \\W=-19.25J[/tex]
Which is negative as it expands against the given pressure.
(b) Moreover, of the process is carried out reversibly, the pressure can change, therefore, we need to compute the work via:
[tex]W=nRTln(\frac{V_1}{V_2} )[/tex]
Whereas the moles are computed from the given mass of argon:
[tex]n=6.56g*\frac{1mol}{39.95g}=0.164mol[/tex]
Thus, the work is:
[tex]W=0.164mol*8.314\frac{J}{mol*K} *305Kln(\frac{18.5dm^3}{21dm^3} )\\\\W=-52.8J[/tex]
Regards.
The work done at isothermal expansion is [tex]19.25 J[/tex] ,The work done where there is reverse expansion is [tex]52.7J[/tex]
From the question, we were givenas[tex](21 dm^3)[/tex]
But the Initial volume increased by [tex](2.5 dm^3),[/tex]
hence final volume= [tex](21 dm^3) + (2.5 dm^3) = 21dm^3.[/tex]
But[tex]1kpa=1000pa[/tex], and [tex]1cm^3=1000dm^3[/tex]
At constant pressure, we can get the workdone asW= -(P Δ V)
If substitute the values we have
[tex]=-[(7.7 *1000pa) *(21-18.5)*(0.001m^3)[/tex]
Then, Workdone [tex]= -19.25 J[/tex]
B) incase there is a reverse expansion, the workdone can be gotten as
[tex]W= nRTIn (V1/V2)[/tex]
[tex]R= 8.314J/mole.K[/tex]
[tex]T=305K[/tex]
we can get the moles from mass of argon and its molar mass. The mass= 6.56g, mm= 39.95gThen number of [tex]mole(n) = (6.56/39.95)* 1 mole= 0.164 mole.[/tex]
Then we can substitute into the formula
[tex]W= - 0.164*8.314*305In(18.5/21)[/tex]
[tex]=-52.7J.[/tex]
Therefore, the work done, when there is reverse expansion is -52.7J
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Plz solve this question..
Answer:
Explanation:
Voltage = 12 (the two batteries are in series and the voltage adds).
Resistance = 3 ohms
I = V / R
I = 12/3
I = 4 amperes.
None of the answers are the right ones. If there is a fifth one that reads 4 amperes then it is the correct answer.
Please help me with this and if I have good answer u will be marked as brilliant !!!!
Bob runs 1800 seconds at an average speed of 1.5 m/sec. How far did he go? 25 Points!!!!
Distance= Time×Speed
= 1800×1.5
= 2700 m
I am not sure it's right. the question itself is confusing.
Two cars A and B with velocity 280m/s and 80m/s respectively, Car B
leaves point X 6:00am and car A also leaves the same point 6:40am
calculate the distance between the two cars after [I] 1hr [ii] where do you
think car A will overtake car B
Car B travels a distance x after time t (measured in seconds) of
x = (80 m/s) t
so that at 6:40 AM (which is 40 min = 2400 s after the starting time of 6:00 AM), it will have moved
(80 m/s) * (2400 s) = 192,000 m
If we take t = 0 to refer to 6:40 AM, the cars' respective positions x at time t are given by
A: x = (280 m/s) t
B: x = 192,000 m + (80 m/s) t
(i) After 1 h = 3600 s, their positions are
A: (280 m/s) * (3600 s) = 1,008,000 m
B: 192,000 m + (80 m/s) * (3600 s) = 480,000 m
away from the point X, so the distance between the two cars is
1,008,000 m - 480,000 m = 528,000 m = 582 km
(ii) Car A moves faster than car B, so A overtakes B as soon as their positions are equal, which happens for
(280 m/s) t = 192,000 m + (80 m/s) t
(200 m/s) t = 192,000 m
t = (192,000 m) / (200 m/s)
t = 960 s = 16 min
So after 16 min, both cars have a position of
(280 m/s) * (960 s) = 268,800 m = 268.8 km
beyond point X.
A Gatorade bottle is dropped on a waterslide. It accelerates at 4.0 m/s2 for 9.0s from rest. What is the slide’s length?
With an acceleration of 4.0 m/s², the bottle attains a speed of
(4.0 m/s²) * (9.0 s) = 36 m/s
so that the slide has length ∆x such that
(36 m/s)² - 0² = 2 * (4.0 m/s²) * ∆x
==> ∆x = 162 m ≈ 160 m
Alternatively, we know the bottle covers a distance ∆x with acceleration a at time t according to
∆x = 1/2 a t²
so that
∆x = 1/2 * (4.0 m/s²) * (9.0 s)² = 162 m ≈ 160 m
Which of the following is true about conduction? Question 2 options: It is heat transfer through direct contact It can only occur in a liquid It is heat transfer in currents through a liquid It is heat transfer as a form of light
Answer:
through direct contact
Explanation:
took the test!
the resistance of a wire the resistance of a wire of length 100 cm and a diameter of 0.3 mm is found to be 3.0 ohms calculate the resistivity and conduct conductivity
Answer:
The resistivity of this wire is approximately [tex]2.1\times 10^{-7}\; \rm \Omega \cdot m[/tex].
The conductivity of this wire is approximately [tex]4.7\times 10^6\; \rm (\Omega \cdot m)^{-1}[/tex].
Assumption: the perpendicular cross-section of this wire is circular.
Explanation:
Convert all unit to standard ones:
Length of this wire: [tex]l = 100\; \rm cm = 1.00\; \rm m[/tex].Diameter of this wire: [tex]0.3\; \rm mm = 3\times 10^{-4}\; \rm m[/tex].Assume that a wire has a resistivity of [tex]\rho[/tex], a length of [tex]l[/tex], and a cross-section area of [tex]A[/tex]. The formula for the resistance of this wire would be:
[tex]R = \displaystyle \frac{\rho \cdot l}{A}[/tex].
Rearrange this equation to find an expression for [tex]\rho[/tex], the resistivity of this wire:
[tex]\displaystyle \rho = \frac{R\cdot A}{l}[/tex].
For the wire in this question, both length [tex]l[/tex] and resistance [tex]R[/tex] are already given. However, the cross-section area [tex]A[/tex] of this wire needs to be calculated from its diameter, [tex]d[/tex]:
[tex]A = \displaystyle \pi\, \left(\frac{d}{2}\right)^2 \approx 7.08\times 10^{-8}\; \rm m^2[/tex].
Calculate the resistivity of this wire:
[tex]\displaystyle \rho = \frac{R\cdot A}{l} \approx \frac{3.0\; \Omega\times 7.08\times 10^{-8}\; \rm m^2}{1.00\; \rm m} \approx 2.1\times 10^{-7}\; \rm \Omega\cdot m[/tex].
The conductivity of a material is the reciprocal of its resistivity:
[tex]\displaystyle C = \frac{1}{\rho} \approx \frac{1}{2.1\times 10^{-7}\; \Omega\cdot m}\approx 4.7\times 10^{6}\; \rm (\Omega \cdot m)^{-1}[/tex].
A body moving in the positive x direction passes the origin at time t=0 . Between t=0 and t=1 second , the body has a constant speed of 24 metres per second . At t=1 second , the body is given a constant acceleration of 6 metres per second squared in the negative x direction . The position at t=11 seconds is?
Answer:
The position at t=11 seconds is -96 m or 96 m to the left of the origin
Explanation:
Constant speed and constant acceleration motion
If a body travels the same distance per unit of time, the body has a constant speed. The equation for the distance x is:
[tex]x=v.t[/tex]
Where v is the constant speed and t is the time.
At time t=0 the body is moving at a constant speed of v=24 m/s in the positive x-direction. It keeps that condition for t=1 sec. The distance traveled is:
[tex]x=24m/s\cdot 1\ s=24\ m[/tex]
Now the body is given a constant acceleration of 6 m/s^2 in the negative x-direction, that is, a=-6 m/s^2
The distance traveled by a body at constant acceleration is given by:
[tex]\displaystyle x=v_o.t+\frac{a.t^2}{2}[/tex]
Where vo is the initial speed and t is the time.
We need to find the position at t=11 sec, but we must subtract the one second already passed, thus t=10 s
[tex]\displaystyle x=24m/s\cdot 10s+\frac{-6m/s^2.(10)^2}{2}[/tex]
[tex]\displaystyle x=240\ m-360\ m=-120\ m[/tex]
This distance must be added to the actual position of the body, that is:
-120 m + 24 m = -96 m
The position at t=11 seconds is -96 m or 96 m to the left of the origin
Which statement best compares and contrasts two physical properties of matter?
Density and solubility are similar because they both involve water, but they are different because density involves dissolving a material and solubility involves floating or sinking a material.
Density and solubility are similar because they both involve a material’s mass and volume, but they are different because density involves floating materials and solubility involves sinking materials.
Boiling points and melting points are similar because they both involve changing the heat of a material, but they are different because boiling point involves adding heat to a material and melting point involves removing heat from a material.
Boiling points and melting points are similar because they both involve the change in a state of a material, but they are different because boiling point involves a change from a liquid to a gas and melting point involves a change from a solid to a liquid.
Answer:
D
Explanation:
Boiling points and melting points are similar because they both involve the change in a state of a material, but they are different because boiling point involves a change from a liquid to a gas and melting point involves a change from a solid to a liquid.
Answer:
D
Explanation:
I answered on eng and got it right
Since illness can be caused by bacteria that live in water, pollution in water can lead to serious illness. true or false
Answer:
true, there are certain forms of bacteria in water that can cause permanent brain damage (although its rare) so further contamination of water can lead to higher chances of contracting serious illnesses caused by such bacteria.
Please help me!!
Two people playing a game of table tennis make up a closed system with 12,175 J of energy. At the beginning of the game the system has 9,875 J of ME and at the end it has 8,430 J of ME. How much of the total energy was transformed into thermal energy during the game?
Answer it's 1,445 A
Explanation:
Basically 9,875 - what will give you 8,430 that's what's its asking. Its just a gap.
Answer:
A
Explanation:
Can someone explain what would happen if you changed something in the past or in the future then time traveled right back to the present day how it would affect the present day.
Answer:
it would affect the present day because you changed what happened so what is happening in present time would be different. think about it this way, our lives right now and what is happening right now is all based on what has happened in the past. If something else were to happen in the past our lives right now would be different.
Answer:
it would affect the present day because you changed what happened so what is happening in present time would be different.
Explanation:
A skier uses a pair of poles to push himself down a ski slope. Which of the following correctly states when the skier has the most potential energy? ( HELP WILL MARK YOU AS BRAINLIEST!!)
a
when the skier is at the top of the ski slope
b
when the skier starts to travel down the slope
c
when the skier reaches the bottom of the slope
d
when the skier comes to a complete stop at the bottom of the slop
The correct statement for the skier has the most potential energy is when the skier is at the top of the ski slope. Hence, option (a) is correct.
What is Potential Energy?Potential energy is a form of energy that is stored but is dependent on the size positions of different system components. Extending or contracting a spring increases its potential energy.
A specimen has much more potential energy when it is raised above the surface of the earth than when it is brought to Earth. It can conduct more work in the raised position. Potential energy is a system property, not a feature of a single entity or particle. For example, the system made up of Earth and the raised ball has greater potential energy as they are far apart.
The potential energy at the top of the ski slope will be maximum, while the kinetic energy at the top of the ski slope will be equal to zero.
Therefore, when he was at the top of the ski slope, the potential energy will be maximum.
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If a set of scores has a mean of 100.00 and
a standard deviation of 5.00, what is the
variance of the standard scores?
Answer:
Variance is 25
Explanation:
Recall that the standard deviation is defined as the square root of the variance. therefore, if you know the standard deviation [tex](\sigma)[/tex], square it and you get the variance:
[tex]Variance= \sigma^2\\Variance= 5^2= 25[/tex]
Select the correct answer.
Mike and Jenna watch a caterpillar form a cocoon. A few weeks later, they watch the cocoon break open and see a butterfly emerge from it. Why does the caterpillar need to turn into a butterfly?
a.to defend itself
b.to excrete waste
c.to have better access to food
d.to reproduce
Answer:d to reproduce
Explanation:
I took the test
Answer:
c
Explanation:
As a gasoline engine is running, an amount of gasoline containing 18,500 J of chemical potential energy is burned in 1 s. During that second, the engine does 3,700 J of work. (a) What is the engine's efficiency (in percent)? % (b) The burning gasoline has a temperature of about 4,400°F (2,700 K). The waste heat from the engine flows into air at about 82°F (301 K). What is the Carnot efficiency (in percent) of a heat engine operating between these two temperatures? %
Answer:
(a) Efficiency = 20%
(b) Efficiency = 88.8%
Explanation:
(a)
The efficiency of an engine is given by the following general formula:
Efficiency = Output/Input
Here, in this case:
Output = Work Done by Engine = 3700 J
Input = Chemical Potential Energy = 18500 J
Therefore,
Efficiency = 3700 J/18500 J
Efficiency = 0.2
Efficiency = 20%
(b)
the efficiency of a Carnot Engine is given by the following formula:
Efficiency = 1 - T₂/T₁
where,
T₁ = Source Temperature = 2700 K
T₂ = Sink Temperature = 301 K
Therefore,
Efficiency = 1 - 301 K/2700 K
Efficiency = 0.888
Efficiency = 88.8%
