Ratio Definition and 1000 Threads

I need to figure out a gearbox ratio to get a 12 inch wheel to travel at 2mph. If I remember right the equation should be 1foot * 3.14*gearbox output rpm*60 then all divided by 5280 to get the final mph. Am I on the right path? Then I need a gearbox output around 58rpm. Thanks to all of...

$\tiny{206.b.46}$ \begin{align*} \displaystyle S_{46}&=\sum_{k=1}^{\infty} \frac{2^k}{e^{k}-1 }\approx3.32569\\ % e^7 &=1+7+\frac{7^2}{2!} %+\frac{7^3}{3!}+\frac{7^4}{4!}+\cdots \\ %e^7 &=1+7+\frac{49}{2}+\frac{343}{6}+\frac{2401}{24}+\cdots \end{align*} $\textsf{root test}$...

Air stops most cosmic radiation. Yet some particles do reach sea level. The cosmic radiation at sea level is estimated at around 300 microsieverts per year. Cosmic radiation also causes nuclear reactions in air that stops it. Many isotopes created by cosmic radiation are stable, or short lived...

A project can be done in 35 days by 12 people. However, after 25 days the project paused for 5 days. How many people need to be added? I guess it's 12. Am I right?

In a class, the mean of boys' mark is 7.1 while the mean of girls' mark is 8.1. Their overall mean is 7.5. If there are 40 students in the class, determine: a. The ratio of boys and girls b. The number of boys and girls I got this question from someone I tutored. I got the number of boys as 24...

Guys,, please check my own way to get Drag coefficient and Terminal Velocity by given Drag force,.. okay,, lets for example: we know drag force is Fd= Cd*pf*v^2*A/2,, ill give little example (Cd=.02)*(pf=1027kg/m^3)*(v^2=.0025m/s)*(A=24m)/2 =( Fd .6162N) so drag force is .6162N,, okay..according...

Homework Statement Rockets are propelled by the momentum of the exhaust gases expelled from the tail. Since these gases arise from the reaction of the fuels carried in the rocket, the mass of the rocket is not constant, but decreases as the fuel is expended. Show that for a Rocket starting...

:D I have trouble in determining the ratio of the area of $\triangle PST$ in terms of $\triangle PQR$ In the triangle PQR $QT=TR$, $PS=1 cm$ , $SQ=2 cm$ , How should I be writing the area of $\triangle PST$ in terms of $\triangle PQR $ [FONT=Arial Black]What is known by me : Since...

I would like to know what gear ratio i would need for my electric longboard. The goal is to run the longboard at 30 - 40 km/h at max power. Me and the longboards weight is approximately 65 kg. The brushless motor i am running has an rpm of approximately 18000 rpm (as it is an airplane engine)...

In the figure , the area of triangle $ABC$ is twice that of triangle $BCD$.USing the given information , find the ration of the area of the triangle $CFG$ to the area of triangle $BEG$ Hint- Use the midpoint theorem. (Wave) Stuck in this problem & currently I have no workings to show.

Homework Statement Given: The amplitude of a damped harmonic oscillator drops to 1/e of its initial value after n complete cycles. Show that the ratio of period of the oscillation to the period of the same oscillator with no damping is given by \frac {T_d} {T_0} = \sqrt {1+ \frac {1}...

Homework Statement A small object with mass m, charge q, and initial speed v0 = 6.00×10^3 m/s is projected into a uniform electric field between two parallel metal plates of length 26.0 cm(Figure 1) . The electric field between the plates is directed downward and has magnitude E = 600 N/C ...

Determine the maximum ratio $$h/b$$ for which the homogenous block will slide without toppling under the action of force F.The coefficient of static friction between the block and the incline is $$\mu_s$$. I have a doubt.About which point should the rotational equilibrium be applied?Should it...

I have $$\sum_{n = 1}^{\infty} \frac{2^n}{n^{100}}$$ and I need to find whether it converges or diverges. I can use the ratio test to get: $$\lim_{{n}\to{\infty}} \frac{2^{n + 1}\cdot n^{100}}{2^n \cdot (n + 1)^{100}}$$ But I'm not sure how to get the limit from this. I know the limit of...

Homework Statement I'm watching this lecture and wanted to attempt to derive the expression for ΔTo/ΔTs Homework Equations ΔTo = ΔTs + VΔTo / U The Attempt at a Solution I have worked out that ΔTs = 1-V / U, however I'm stuck trying to get ΔTs / ΔTo because of the ΔTo on both sides of the...

Sorry in advance if I've posted in the wrong section. given the set ##\{r_i, r_{ii}, r_{iii}, ... , r_R\}## where ##r \ \epsilon \ \mathbb{Z}_+ \ , \ r_i \geq r_{i+1}##How would you go about finding the bounds of something like this, or determining if it even has any? ##( \...

Homework Statement If 15 workers can pave 18 driveways in 24 days, how many days would it take 40 workers to pave 22 driveways Homework Equations Actually i don't know which equation should be used for 3 quantities. I know the eq for two quantities. Because we increasing labours so we would...

Hi Air conditioner vs evaporative cooler: ratio of (BTUs/hr) / electrical watts I know evaporative coolers do not state BTUs/hr. I do not know why. Did anyone try them and record time taken to cool. I found this example, but I do not know if it is practically relevant...

If you divided the circumference of an infinitely large circle by its diameter, would the result be pi?

Hello, I have a set of N samples, each of which yields the measurable variables A and B. I am interested in computing the mean and standard error of the ratio A/B within the group. The catch is that I need to do background subtraction on both A and B, and the two different background values BGA...

Homework Statement Determine the conditions of a continuous ratio knowing that the product of the four terms is 1296 and the last term is equal to 1/6 of the sum of means. Original question (in Portuguese): Determinar as condições de uma proporção contínua sabendo que o produto dos quatro...

Hi everyone, first time poster here, I'm studying for a Materials exam, one of my weakest subjects and this question is causing me a lot of pain: Beryllium (Be) is a HCP metal with an atomic weight of 9 g mol-1 , an atomic radius of 0.112nm and a density of 1850 kg m-3 . Calculate its c/a ratio...

Hello, Can someone tell me the optimum stoichiometric air/fuel ratio of gasoline VAPOR? I know that with liquid gasoline the optimum stoichiometric air/fuel ratio is 14.7 parts ambient air to 1 part gasoline. Thank you in advance for your help.

I have no idea how to solve this problem. ABCD is just an irregular Quadrilateral so nothing too special with that figure. We are looking for the ratio BC:CD and we only have that two angles. I know that the answer is 1:√2, but I have no idea how to find it.

hi, If you look at my attachment you can see that the book express that for the situation of x=+,-(1/L) we need further investigation. It means being converged or diverged is not precise. I would like to ask: Is there remarkable proof that if x=+,-(1/L) convergence or divergence is not...

Homework Statement 4. Two bodies of mass m1 and m2 have equal momentum their kinetic energies E1 and E2 are in the ratio. ans. m2 : m1[/B]Homework Equations E1=E2 P= mv The Attempt at a Solution E1=E2 1/2M1v^2=1/2M2v^2 (Mv^2)/2=(M2v^2)/2 multiply both side by 2 mv^2=2(m2v^2)/2 mv^2= m2v^2...

Homework Statement a gemoetrical similar open chanel model is constructed with 10: 1 , if the model discharged 7m^3 /s , what is the corresponding discharge in prototype? Homework EquationsThe Attempt at a Solution Q = (L^3) / T , [ (Lp^3)/ (Tp) ] / [ (Lm^3) / Tm ] = (Lr^3) / Tr [/B] but...

Hi, Just made a small thought experiment on the train, haven't really thought about it in depth. I was just wondering, if I created the above scenario (open circuit secondary and a voltmeter), would I get a voltage (assuming there is a difference in turns for primary and secondary)? Neglecting...

hello everyone, i would like please to know what is Effective Compression Ratio for an RC 2stroke Engine that i have ? the value in the info is 9.7, so i need to know the meaning and what values are the best ? what is the range ?

I'm conducting an experiment in order to find the effectiveness of dimples in a golf ball when flying through the air. As part of the experiment, I'm planning on testing the different dimple patterns of various golf balls. However, I'm having trouble coming up with a numerical ratio that can...

I want to know how mathematician got the idea of external division , how they can say that a point can divide a line externally, what's the reason behind this discovery . Why they discovered it.

Homework Statement Two crates are stacked on top of each other on a horizontal floor. The coefficient of static friction between Box A and Box B is 0.6. The coefficient of static friction between Box A and the floor is 0.2. A force of 100 N is applied parallel to the floor on Box B. The boxes...

Homework Statement A ball rolls down an incline plane without slipping. What is the ratio of its angular velocity at h/3 to its angular velocity at 2h/3? 1) 1:2 2) 1:sqrt(2) 3) 1:1 4) sqrt(2):1 5) 2:1 Homework Equations Conservation of energy with provisions for rotational and...

Firstly, let me explain that I am mostly inept at mathematics. Piecing together the required information is becoming a real challenge because of that. I am motorizing a dobsonian telescope. I have read many accounts of success and the steps involved. The places where detail is commonly left out...

For any rod Poisson's ratio should be same i.e. 0.5 (we get this ans if we find (dr/r) / (dl/l) ) assuming that volume of rod always remains constant... But why it is not so ? We have different ratios for different materials..

Homework Statement A Grand Prix race car accelerates to twice the speed of the car in sample problem 1, in the same amount of time. Calculate the ratio of the power needed by the Grand Prix car to the power needed by the car in sample problem 1. Given: initial speed of car=0m/s, final speed...

Homework Statement If the relative noise (noise divided by signal) in a region of a CT slice is measured to be N what would be the value if the tube current was halved, the pitch increased from 0.9 to 1.2, the rotation time increased from 0.75s to 1s and the slice width increased from 1mm to...

Homework Statement Let f(x)= (1+x)4/3 - In this question we are studying the Taylor series for f(x) about x=2. This assignment begins by having us find the first 6 terms in this Taylor series. For time, I will omit them; however, let's note that as we continuously take the derivative of this...

Prior to my life as a database administrator I was a hi lead logger in coastal British Columbia, which involves harvesting logs with machines capable of putting huge strain on cable and hydraulic systems. What got me to thinking this was a friend just let me know someone we know was recently...

Homework Statement A car traveling at an unspecified constant speed passes a parked motorcycle cop. The motorcycle accelerated at an unspecified constant acceleration and reaches the car at unspecified distance d. At what point did the motorcycle's speed match that of the car, expressed as a...

Hello, I'm making a fire-boat. The boat uses 2L bottles to supply water. The fire will be 1m from the fire fighting zone and 0.5m high. The bottles are pressurized to 300 kPa. How do I maximize the volume-pressure ratio that can be supplied at that range over 90s maximum?

So, great site. I have a quick question that I think has a simple answer. On a snowmobile forum I visit there has an ongoing debate. The question is, all other factors being the same, does changing the lug height on a track, change the final drive ratio of the snowmobile? I think I know the...

Hey Guys, So in the attached image I'm trying to determine what the rpm of the 60 tooth gear will be given the 8.4" tire will be rotating at .68 rpm, everything else is just an assumption on my part. I'm assuming the following which is probably wong: The tire being rotated at .68 rpm will...

Hi if I had the ratio of 4:1 and the frequency of 10Khz how would I go about finding the time?

I was wondering if there is a current hypothesis about the quantities of which matter particles were created? I'm not completely au fait with the standard model, but I've seen the picture...

Two corresponding sides of two similar polygons have lengths 3 and 7. the perimeter of the larger polygon is 91 cm. What is the perimeter of the smaller polygon? What is the ratio of their areas? I believe I have found the perimeter of the smaller polygon (39), but I can't figure out the areas...

Alan is a jogger that leaves the top of a hill heading for the bottom of the hill. At the same time, Jenny, a biker, heads up the hill attempting to reach the top. They each proceed at a steady rate. After passing each other, Jenny takes 81 times as long to reach the top as Alan takes to reach...

Homework Statement where does the 1(circled part) come from ? is it a mistake ? Homework EquationsThe Attempt at a Solution

Hi all. I'm in need of a formula to calculate (roughly) the percentage of an ammonia-water mixture (arbitrary ratio of ammonia to water) that will boil off under different pressure/temperature conditions, in the ballpark range of 0.2-1.3 bar and 220K-350K. I don't necessarily need to know the...

Hello, can anyone help please? Many thanks! 'Jing set a goal of hitting 9 home runs.When the season was over,she had hit 12 home runs.Express the portion of her goal Jing reached as a fraction,a decimal,and a percent.Round to the nearest whole percent.'