Efficiency Definition and 950 Threads

Homework Statement Alright for this thing, we had to pull a cart up a inclined plane and time how long it took to get to the bottom. Distance from ground to top of inclined plane is - 0.125m Length of Board is - 1.21m Mass of cart - 1.09kg Force to pull cart up - 1.4N Time it took for...

Homework Statement There are two Carnot engines in series, so that the heat exhaust from the first engine drives the second. Find the overall efficiency of the arrangement which contains only the efficiences of the individual engines. Homework Equations \epsilon = \frac{W}{Q_{input}}...

Hey How can i calculate the amount of energy/power required to accelerate my roller coaster on a flat track. Mass=4500 approximate when loaded Time=2.64secs to reach top speed Distance=125m Velocity=47.248ms-1 I know how to calculate it for a track that rises i can use M*G*H/Time but my...

Hey, I recently read that they made a 40% efficient solar cell... what does this actually mean? How do they calculate this efficiency... and how much power do these cells actually produce? and what's with the mono and poly crystalline titles that they get? what does that mean?? Any info...

Homework Statement Suppose 1.0 mol of a monatomic ideal gas initially at 10L and 302K is heated at constant volume to 604K, allowed to expand isothermally to its initial pressure, and finally compressed at constant pressure to its original volume, pressure, and temperature. (c)What is the...

for my A level coursework i am doing the efficieny of a motor, I've just about sussed the theory:confused: . Now i have found out that the efficieny increases as the voltage increases and its wrong! :mad: i need help on saying why this would be the case. help would be much appreciated!

I'm doing an experiment (at A-Level) to see the efficiency of a wind turbine. I'm doing this by changing the number of blades and varying the wind speeds. I wondered if anyone had an equation that could look at efficiency? I have the current and the voltage (and wind speed). Sorry if I've...

Homework Statement I am doing a lab experiment and the objective is to find the efficiency of an elastic band. Distance to ceiling=2.9m Mass of elastic band= 1.85g Force 2.6N (found using Newton meter) Extension: 6.4cm Homework Equations Well I am not looking for a solution, I...

I'm very excited. I just finished ordering all the necessary parts to install a solar water heating system. With the likelihood of electricity only getting more expensive, coupled with the likelihood of my 3 children getting bigger, It seemed like a no-brainer. Who else has solar heat...

strange question efficiency if a human does pushups , it is an oscillatory motion and no work was done. efficiency which is defined as e= useful energy output/energy input is 0. But since you burn a lot of atp and calories, can the efficiency coefficient be a negative value?

There's a debate these days related to the australian ban of traditional light bulbs, because of the loss of heat energy: http://www.ens-newswire.com/ens/feb2007/2007-02-21-01.asp" But in a colder place than Australia (like Norway), it think this number would be lower than 66% because some of...

I think the 2nd law of thermodynamics, which places limits on the efficiency of thermal engines, can also be interpreted as saying increasing efforts to improve efficiency result in geometrically decreasing results. I can't find that stated, though. I suppose it's just the first derivative...

(Hope this is in the right forum) For my A Level coursework I have to do a practical investigation. I'm thinking of doing one looking at the efficiency of a siphon. One relationship I am going to be looking at is the rate of flow vs height (difference between the two water levels). Now...

(ok i not sure where this topic goes so ill take a guess its here) ok, I hear that nothing is 100% efficienct. some energy is always lost as heat and sound. however, what about heating elements? or electrical heats or whatever, surely the lost heat (and i don't think any sound cause its...

A reversible heat engine has an efficiency of 34.2%, removing heat from a hot reservoir and rejecting heat to a cold reservoir at 0°C. If the engine now operates in reverse, how long would it take to freeze 1.10 kg of water at 0°C, if it operates on a power of 183 W? I am getting stuck...

An engine releases 0.490 kJ of heat for every 0.120 kJ of work it does. What is the efficiency of the engine? I am having trouble with this problem. I tried Wnet/ heat input = efficiency 0.120/0.450 = 0.27 but it says it is the wrong answer. (correct answer is 0.21)

Homework Statement A 0.45 µF capacitor is charged by a 1.5 V battery. After being charged, the capacitor is connected to a small electric motor. Assuming 100% efficiency, to what height can the motor lift a 4.7 g mass? Homework Equations I really need some direction to start off this...

Question: what is the range for propeller efficiency for plastic toy propellers?

Homework Statement Could I please have a tutor check my answer and solution? question: An effort of 3 kN is required to move a mass of 2000 kg in a certain simple machine. If the mass is raised 1.5 meters while the effort moves 12 meters, find the efficiency? [b]2...

First off I want to say thanks to all of those who help begineers like me out on this board...but anyways...:cool: In lamens terms, what is volumetric effeciency...how can one go above and beyond 100%. I was asking, because I looked at a dyno graph of a higher revving 302 (8,000 rpm)...

Homework Statement I've calculated the time, the distance, the height of the counterweight before launch, the mass/weight, and I need to calculate the energy efficiency. How to go about it? h = 0.71 m m = 1.445 kg g = 9.8 m/s^2 t = 0.7 s x = 4.44 m Homework Equations Eg = mgh Vix = x/t y =...

Suppose it takes 48 women 16 days to do the same job that it takes 16 men to do in 24 days. If 10 men started working on the job and worked for 5 hours, then all 48 women joined them. how long would it take them working together to finish the job? i know i have to find the rates so i have...

Homework Statement Suppose that two heat engines are connected in a series, such that the heat exhaust of the first engine is used as the heat input of the second (attached diagram below). The efficiencies of the engines are e1 and e2, respectively. Show that the net efficiency of the...

Homework Statement Calculate the maximum possible efficiency of a heat engine that uses surface lake water at 18.5°C as a source of heat and rejects waste heat to the water 0.100 km below the surface where the temperature is 4.3°C. Homework Equations e=1-Qc/Qh Q=cm(deltaT) The...

A 100-hp car engine operates at about 15 percent efficiency. assume that the engine's water temperature is 85deg C is its cold-temperature (exhaust) reservoir and 500deg C is its thermal "intake" temperature (the temperature of the exploding gas/air mixture) a)calculate its efficiency...

what is pde ? in terms of the formula , and in general so i can picture it in my mind so to speak.

Here I describe one mechanical engineering situation that is very useful in any kind of mechanical and energy consumed industries.I hope you will try to understand it and use it. If you find any difficulty to understand ,feel free to ask me. we can increase efficiency of rotating shaft...

We are developing an engine with pistons and cylinders that do not reciprocate... in other words the inertia of the pistons is constant at a given engine speed. More on that latter if you wish. We are looking for a method to calculate the efficiency losses in a conventional internal...

A nuclear power plant generates 500MW at 34 percent efficiency. The waste heat goes into the connecticut river with an average flow of 3x10 to the 4th kg/s. How much does the water temperature rise? (it requires 4.8x10 to the 3 to raise the temperature of 1kg of water 1K

what is the equation for the mechanical efficiency of an internal combustion engine? what are the formulas for 'ip' for 4-stroke and 2-stroke engines? thank you

Hi all! How do we define the power of a pump? I read a formula from a book which defines the power of the pump as follows: Power of the pump = Maximum back pressure * maximum flow rate / 2 Can anyone explain why the right hand side equals the left hand side? I don't understand why the...

Hi guys, could someone help me on this? I'm stuck :( *A motor draws 35kW electricity, it operates at 90% efficiency. The motor is connected to an oil pump which has an inlet diameter of 8cm & an outlet diameter of 12cm. pressure rise in the oil pump is 400kPa. oil enters the pump at 0.1m^3/s...

Hi guys, could someone help me on this? I'm stuck :( *A motor draws 35kW electricity, it operates at 90% efficiency. The motor is connected to an oil pump which has an inlet diameter of 8cm & an outlet diameter of 12cm. pressure rise in the oil pump is 400kPa. oil enters the pump at 0.1m^3/s...

Appreciated members of this forum: Suppose we have an infinite set of n carnot cycles and we know the efficiency of each cycle of the set: E1,E2,E3,E4,E5,,,,,En , where En is the efficiency of the nth cycle. E1= 1-Ta/Tb1 , E2= 1-Ta/Tb2, E3= 1-Ta/Tb ... En=1-Ta/ Tbn Ta is the...

I've some ZnO films grown on sapphire substrate. The ZnO film, however, is a highly-oriented polycrystalline film. The annealing was carried out at 800'C at different ambient, (N2, O2, etc.) After annealing, as expected, the crystallinity improved (narrowing FWHM of XRD). Resistivity...

f an engine must do 500 joules of work to pull a 10 kg load up to a height of 4 meters, what is the efficiency of the engine? So that's 400/50,000 which gives me 0.008 Does that mean the efficiency is 8%?

The burning of gasoline in a car releases about 3.0 x 10^4 kcal/gal. If a car averages 41 km/gal when driving 90 km/h, which requires 25 hp, what is the efficiency of the engine under those conditions? I think I have an answer, but I'm not sure if it's correct. 1 horsepower = 746 watts...

In an assigment I'm using the general formula P=F*v, where P is the effect of a motor. The motor drives something through a series of sprockets, who's efficiency is 85 %, and so it seems intuitive to me to multiply the resulting P with 0,85 to get true effect, but apparently the solution divides...

I've always heard (from professionals as well) that each step in a food change has a roughly 10% efficiency rate. That is, you earn 10% of the energy the lower chain animal/plant earned when it ate/did whatever. Now my question is in regards to what you hear a lot of hippie-types say: Humans...

It was my logic that efficiency should decrease as the amount of pulleys introduced into a pulley arrangement increased. This is since the amount of places where frictional resistance can occur is greater. Therefore, as TMA increases, i would expect Efficiency (AMA/TMA) to decrease...

Suppose you had the choice of either raising the high-temperature reservoir a certain number of kelvins, or lowering the low-temperature reservoir the same number of kelvins. Which would you choose (assuming you wanted to increase the efficiency, of course)? After doing experimenting with...

please help me in cllecting information about High Temperature Superconductor motor. Are they available in the market? how effecient are they? I need to know all their details, properties, design, advanteges. Thanks all

I was looking through product info this morning and noticed (it got no press that I saw) that the DOE, after a protracted battle with the HVAC industry, started enforcing its new 13 SEER (up from 10 SEER) energy efficiency standard for all new a/c units sold in the US. The primary...

In one cycle, a heat engine absorbs 520J from the high-tempt reservoir and expels 390J to a low-tempt. reservoir. If the efficiency of this engine is 68% of the efficiency of a Carnot engine, what is the ratio of the low tempt. to the high tempt. in the Carnot engine? e=1-(390/520)=.25...

In a home heat pump, heat is absorbed from the Earth by a fluid circulating in buried pipes and delivered to the home interior. Suppose that the heat pump is 40% as efficient as a Carnot refrigerator. If the ground surrounding the pipes is at 5`C and the interior temperature of the house is kept...

What is the actual gain in efficiency in a hybrid?

Hi, I'm trying to calculate the efficiency of fuels such as gasoline, diesel, methanol, and ethanol. I have collected several properties such as energy content per gallon (btu) and densities for each fuel. I'm a bit confused as to how i can calulate these fuels' efficiencies...

A 3.25 * 103-kg aircraft takes 12.5 min to achieve its cruising altitude of 10.0 km and cruising speed of 850 km/h. If the plane's engines deliver, on the average, 1500 hp of power during this time, what is the efficiency of the aircraft engines? I initially believed the power out would be...

I have two problems on permutations which I can´t solve now becuase my knowledge about permutations and the necessary tricks is very poor. 1st: Find an algorithm that for given natural N (N<=1000), K and given permutation of N elements will find the Kth composition of this permutation in time...

I've calculated the efficiency of the Stirling cycle like \eta=\frac{R(T_H-T_L)\ln\left(V_2/V_1\right)}{RT_H\ln\left(V_2/V_1\right)+C_{mV}(T_H-T_L)} Where V_2>1. It's also derived http://www.pha.jhu.edu/~broholm/l39/node5.html" . But my ("Highschool", or secondary school) teacher says...