Calculating Work Output from Thermal Efficiency of Car Engine

  • Thread starter Thread starter WhyPrime89
  • Start date Start date
  • Tags Tags
    Efficiency Thermal
AI Thread Summary
To calculate the work output from a car engine's thermal efficiency, the power output of 600 kilowatts per hour must first be converted to kilojoules per second. The thermal efficiency formula, which is work output divided by heat input, indicates that only 30% of the energy is converted to work. The confusion arises from the interpretation of the power output, which reflects energy loss, suggesting that the initial energy input is higher than the output. Correct calculations involve adjusting for efficiency and understanding the relationship between power, work, and energy loss. Properly applying these concepts will yield the correct work output per cycle.
WhyPrime89
Messages
3
Reaction score
0

Homework Statement


The power output of a car engine running at 1900 is 600 kilowatts per hour.
How much work is done per cycle if the engine's thermal efficiency is 30.0 percent

Homework Equations



thermal efficiency=w(out)/Q(hot)

The Attempt at a Solution


It wants the answer in KJ/s so i converted the kilowatts to KJ/sec then divided by rev/s then multiplied by .3. What am i doing wrong? Any help would be appreciated.
 
Physics news on Phys.org
Looks like you should be multiplying by 10/3.
The 600 kw/hr seems to be the power output after 70% of the initial energy has been lost.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Thermodynamics Problem: Calculate the heat input for this work output
Replies
17
Views
4K
Thermal efficiency of the engine in a PV diagram
Replies
2
Views
3K
Calculating Efficiency and Work in Otto Cycle Engine
Replies
1
Views
1K
Heat Extracted and Delivered to Reservoirs in a Heat Engine
Replies
7
Views
2K
Thermal efficiency of a heat engine
Replies
3
Views
2K
Calculating Heat Engine Efficiency: What is the Energy Input?
Replies
2
Views
2K
Calculating Efficiency and Thermal Source Rate in a Steam-Electric Power Plant
Replies
4
Views
3K
Calculate Thermal Indicated Thermal Efficiency Of An Otto Engine
Replies
1
Views
9K
How to calculate the efficiency of a fuel engine
Replies
2
Views
3K
Calculating the Efficiency of a Heat engine
Replies
32
Views
4K

Hot Threads

Recent Insights

Back
Top