Efficiency Definition and 950 Threads

I need to explain why, in our tests, the efficiency of our slingshot device remained constant when the angle of launch was changed and the extension (how far the rubber band was pulled back) was constant. Basically it was a 1m long wooden plank held up on bricks, with a rubber band attached...

I know a heat engine can never be 100% efficient. There has to be a cold reservoir that some of the heat is rejected to. Why is that? I know it is because of entropy, but could someone please provide some further explanation. Thanks.

Hi, I have a rubber bouncy ball which is shot off a ramp using a rubber band slingshot. I've calculated the ideal range, and then measured the real range. By dividing the real by ideal and multiplying by 100, I get a 51% efficiency. Does that sound viable? How else can I measure the...

My question involves heat engines. I understand that a heat engine typically uses energy provided in the form of heat to do work. According to the 2nd law of thermodynamics, however, not all heat energy can be converted into work energy, meaning that heat engines are not perfect. At least some...

Is it possible (at least theoretically) to construct engine which uses Carnot cycle and two reservoirs with temperatures T_1<0<T_2 (one of them has negative temperature which is possible e.g. in case of two-state paramagnet). Such cycle would have efficiency greater then 1. (of course the...

when approaching C the mass of your craft increases. If the mass of your fuel increases also wouldn't that mean the faster you go the more fuel youll have?

currently, I'm be studying on improving fire tube boiler's combustion efficiency. so, i need a software which is applicable to the title above in order to prove my calculation according to the formula. can u tell me what software can be used?

Hello, I just saw something that is a bit confusing to me and i hope someone could explain the difference. I read something about an energy production system design and there are some calculations including some losses of the system. Taking into account the inverter losses, let's say for...

This seems pretty hard to do but is there a way to figure out how efficient a vehicle is based on fuel used and MPG? I know there's about 1/3 gone to exhaust 1/3 through radiator and 1/3 is work but I want to get an exact percentage on the work part. So it would be 33% if it was like what I...

The new issue of the mechanical efficiency of the new 4 stroke engine.What will have the efficiency of the engine, which increases its volume swept by two times slower rotating crankshaft- piston systems ?? Two times slower or inertia four times smaller. Regards Andrew

Homework Statement A working substance goes through a cycle within which the absolute temperature varies n-fold, and the shape of the cycle is , where T is the absolute temperature, and S the entropy. Find the efficiency cycle. Homework Equations \frac{\delta Q_R}{T}=dS...

Greetings physics gurus Im getting bogged down on conversion of the VA to A Homework Statement A small transformer used to power a laptop computer has the following characteristics printed on it: • input AC 220 V, 50 Hz, 15 VA. • output DC 5.0 V, 1.0 A. Is this transformer...

We all know that there are several options of front sprocket/rear sprocket combinations that achieve the same gear ratio. i.e. A large front sprocket with medium rear or medium front with larger rear will produce the exact cadence at a given speed. What I've always wondered, is there any...

hey, I was reading Aircraft Design: A Conceptual Approach by Raymer and i came across the following line. ' The aerodynamic efficiency of an aircraft, expressed as the lift to drag ratio is greatly reduced during low level, high speed flight as well is its engine efficiency. ' Can someone...

I have been having difficulty finding information regarding Linear Generators, maybe they have not been used enough and are begininning to be sought after more for renewable energy production. Back to the title, does anyone know approximately the efficiency of a linear generator, or at...

I have two questions/ideas about the efficiency of A/C's that I'd like to bounce off you guys. I couldn't find anything on Google about either of these items being discussed before. 1) Precooling The first thought I was wondering was whether it was more efficient to pre-cool your house in...

I understand that generating the hydrogen that powers a typical fuel cell is (prohibitively?) energy intensive at this point, but I was curious about the following: Assuming a sufficiently efficient catalyst was obtained that allowed large-scale production of pure hydrogen without...

Hey. I am currently doing a bit of revision for an exam and I am struggling on the following question: I understand the whole voltage/current/power/impedance ratio stuff, but can't seem to find any information on calculating efficiencies using the resistances or the transformer core losses...

I want to estimate the efficiency of SFG in a BBO crystal for the situation when one pulse has much higher energy than the other (nJ compared to fJ), and the beams cross at an angle in the crystal. Can anyone recommend a resource that would help with this?

Homework Statement How would you find the energy efficiency of a torsion catapult ? (one i built for project) I have the Force at which I am pulling the arm. F = 20N also the angle from origin to the point of release ( or when the ball leaves the arm) Theta = 50 degrees...

Homework Statement List 2 major factors result in an efficiency of less than 100% when using an inclined plane to raise a mass Note - this is a grade 11 lab so don't have answers that are too advanced please :DHomework Equations eff = eout/ein x 100% ... = mghf/fd x 100%The Attempt at a...

Homework Statement Homework Equations N/A The Attempt at a Solution I have been struggling with these questions for the past week, with not much result at all. I have to study at home, through the use of various textbooks, and with no teacher to guide me through the process...

Homework Statement In an ideal case of pulling a cart up a ramp where there is no friction should the efficiency be less than that of pulling a cart up a ramp with friction?Homework Equations W=F\DeltaXcos\theta Efficiency=(work output/work input)*100 The Attempt at a Solution I was trying to...

Homework Statement The electric output of a power plant is 750 MW. Cooling water flows through the power plant at the rate 1.0*10^8 L/hr. The cooling water enters the plant at 16 degrees C and exits at 27 degrees C. What is the poer plant's thermal efficiency? Homework Equations W =...

When I got my motorbike it had a non-standard rear sprocket with two extra teeth. I decided to swap it for a standard one. I expected to get a better overall mpg, but it didn't change noticeably. So... An engine has a red line at 14000 rpm. Peak power is delivered at 12000 rpm. Driving...

Hi everyone, Somewhere I've heard of a special type of laser which when it strikes matter could convert near 100% of it into energy, the laser's energy being insigificantly small as compared to the output thus achieving ~100% efficiency? Is this a way or is there any other means to achieve...

Homework Statement (c13p30) A steam-electric power plant delivers 900 MW of electric power. The surplus heat is exhausted into a river with a flow of 6.29×10^5 kg/s, causing a change in temperature of 1.03 oC. What is the efficiency of the power plant (in % Don't enter a unit.)? Homework...

Homework Statement i have an mechanical engineering problem. A gas taken thru a 4-process cycle has 1-2 isothermal volume ratio rv,2-3 isobaric constant pressure,3-4 isentropic reversable adiabatic and 4-1 isochocric constant volume. How do i formulate the thermal efficiency equation for it...

Independent variable and spring constant k Hi all, If someone could spare a minute to help answer my question I would appreciate it greatly, I am trying to design an experiment to investigate the efficiency of a catapult, But need help in what i should use as the independent variable-...

i will make an report about the propeller efficiency can anyone help me and tell me the things i need to put in this report and the references i can use

Help with a catapult Homework Statement Hi all I have design a prac to investigate the efficiency of a catapult, was wondering if anyone could shed some light into this area Homework Equations Ee=0.5kx^2 (hookes law) The Attempt at a Solution I was thinking that my independent...

Now i am doing study on vessels propeller efficiency which i can determine the best time to do propeller polishing.Do anyone have any idea on how do i calculate this propeller efficiency

Homework Statement Hey guys! I am doing a very simple lab, and in need of your expertise! Haha, I am an intro-physics student, please don't get too complicated with me, my knowledge is very limited. The QUESTION is: WHAT IS THE RELATIONSHIP BETWEEN EFFICIENCY VS HEIGHT...

Hello; Is there a 100% efficient component? One where there is no waste energy? Or something that is completely renewable such that all the energy wasted is put back into the component?

This is a very quick question but in the equation e=1-Q_{C}/Q_{H} do we treat both Q's as positive even though heat goes in in one case and out in the other? Or is there some detail I'm missing that would otherwise make the result less than 1.

I'm trying to reproduce the plot in the attached figure. I know the band-gap energies, so I was hoping there was some simple way I could get the quantum efficiency as a function of wavelength. I read on wiki that Energy(eV) = 1240/wavelength(nm), so I mechanically plugged those in, and got...

Homework Statement A Student Performs an experiment in which an electric motor is used to lift a 200g weight through 2m, thus increasing its potential energy by 4j. From measurements of the rate at which the weight is lifted the efficiency of the motor is to be determined. Two different...

The theoretical maximum efficiency of silicon solar cells is about 29%. How is this theoretical maximum efficiency derived? How can I use the working principles of a silicon solar cell to explain this?

for a given volume of gas,is it more efficient to compress smaller volumes of gas more no. of times or compress large volumes of gas less no. of times?

I'm observing the circular process of a heat engine. It's p-v diagram is So between points 3 and 4 the heat is extracted. That causes losses since the efficiency if given by \eta =1- \frac {Q_c} {Q_h} Where Qh is the heat the heat source has given and Q_c the amount of heat that...

Homework Statement The specifications of a transformer for a small appliance read "Input: 110 V, 6.4 W" and "Output: 8.9 V, 270 mA". What is the efficiency of this transformer? Homework Equations P = I * V V = I * R The Attempt at a Solution 6.4 W / (8.9*(270*.001)) ---> I think this is...

Homework Statement http://img291.imageshack.us/img291/7786/effx.jpg Homework Equations e=1-1/(V1/V2)^(gamma-1) The Attempt at a Solution This is a practice test where he gives the solutions, as you can see the first thing he asks for is the efficiency, and lists the answer as...

What is the efficiency of the latest photovoltaic panels and also wind turbines? I read in an article that the highest efficiency reached by photovoltaic panels was around 40%, which seems to be very very high.

Efficiency of Ejector "as pump" I was asked to find the efficiency of a steam ejector experiment "as a pump". So I tried the formula : [(m(P/density + V^2/2))discharge - (m(P/density + V^2/2))suction]/ (m(P/density + V^2/2))steam inlet. I am getting an efficiency of 0.5%. Is this a...

Hi all, Got a bit of a problem with a lab experiment at uni (I'm not sure if this is the right place to post this, mods feel free to move it if necessary!) Anyway: We're trying to get a plot of efficiency against energy for a planar germanium detector. We've got spectra for different...

Homework Statement One rechargeable battery of mass 15.0 g delivers to a CD player an average current of 15.5 mA at 1.00 V for 2.50 hr before the battery needs to be recharged. The recharger maintains a potential difference of 2.00 V across the battery and delivers a charging current of 10.0...

Homework Statement On a hot day a house is kept cool by an air conditioner. The outside temperature is 32°C and the inside temperature is 21°C. Heat leaks into the house at the rate of 9000 kcal/h. If the air conditioner has the efficiency of a Carnot engine, what is the mechanical power that...

The medieval trebuchet is a missile-throwing device, with a heavy counterweight on the short end of a beam that pivots about an axle fixed to a supporting frame. A sling is attached to the long end, and when properly "tuned" by adjusting its length, it will release the missile at exactly the...

A question regarding power supply efficiency: The theoretical maximum efficiency of a full-wave rectifier circuit with a resistive load and no smoothing is around 82%. In the calculations to derive that the resistance of the source or the rectifiers does not enter into the equation, so the...

I am currently in the process of writing a program in VBA that will numerically "solve" a given n-body gravitational problem. I'm doing this pretty much just for fun and am by no means a programmer (had a 1 semester course in c++). The question I have is something that seems to keep coming into...