Internal-Combustion Engine Prototypes Ranking Task?

  • Thread starter Thread starter cupcake
  • Start date Start date
  • Tags Tags
    Engine Ranking
Click For Summary

Homework Help Overview

The discussion revolves around ranking internal combustion engines based on their designed power output and thermal efficiency. Participants are analyzing given values of heat input (Qin), heat output (Qout), and frequency (f) to derive power output and efficiency metrics.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are calculating power output using the formula P=Work/t, where Work is defined as Qin-Qout and t is derived from frequency. There are questions regarding the correctness of these calculations and the application of thermal efficiency in their rankings.

Discussion Status

Some participants have shared their calculations and rankings, but there is uncertainty about the accuracy of these results as they have been flagged as incorrect by an external source. The conversation includes requests for clarification on thermal efficiency and its implications for the problem.

Contextual Notes

There is mention of a specific platform, Mastering Physics, which may impose particular requirements or constraints on the problem-solving approach. Participants are also discussing the thermal efficiency formula, indicating a need to consider it in future rankings.

cupcake
Messages
73
Reaction score
0

Homework Statement




Rank these engines on the basis of their designed power output and their thermal efficiency.

1) Qin = 3000 J, Qout = 1500 J, f=150 Hz.
2) Qin = 4000 J, Qout = 3000 J, f=50 Hz.
3) Qin = 1000 J, Qout = 200 J, f=200 Hz.
4) Qin = 2000 J, Qout = 500 J, f=50 Hz.
5) Qin = 2000 J, Qout = 1000 J, f=100 Hz.
6) Qin = 1500 J, Qout = 500 J, f=200 Hz.

Homework Equations



P=Work/t, and Work=Qin-Qout

The Attempt at a Solution



I calculated the power output using the above formulas, where t=1/f, but I don't know why my answers are wrong... this is mastering physics question :(
 
Physics news on Phys.org
cupcake said:

Homework Statement




Rank these engines on the basis of their designed power output and their thermal efficiency.

1) Qin = 3000 J, Qout = 1500 J, f=150 Hz.
2) Qin = 4000 J, Qout = 3000 J, f=50 Hz.
3) Qin = 1000 J, Qout = 200 J, f=200 Hz.
4) Qin = 2000 J, Qout = 500 J, f=50 Hz.
5) Qin = 2000 J, Qout = 1000 J, f=100 Hz.
6) Qin = 1500 J, Qout = 500 J, f=200 Hz.

Homework Equations



P=Work/t, and Work=Qin-Qout

The Attempt at a Solution



I calculated the power output using the above formulas, where t=1/f, but I don't know why my answers are wrong... this is mastering physics question :(
Perhaps you could show us your answers. What is your equation for thermal efficiency? Are you taking that into account?

AM
 
so,

1) W1=1500 P1=W1/t= 225000
2) W2=1000 P2=W2/t= 50000
3) W3=800 P3=W3/t= 160000
4) W4=1500 P4= 75000
5) W5=1000 P5=100000
5) W6=1000 P6=200000

so, the rank from the largest to the smaller will be, P1 > P6 > P3 > P5 > P4 > P2

thermal efficiency formula is 1-Qin/Qout, that one is for the next question (arrange by basis of thermal efficiency)
 
cupcake said:
so,

1) W1=1500 P1=W1/t= 225000
2) W2=1000 P2=W2/t= 50000
3) W3=800 P3=W3/t= 160000
4) W4=1500 P4= 75000
5) W5=1000 P5=100000
5) W6=1000 P6=200000

so, the rank from the largest to the smaller will be, P1 > P6 > P3 > P5 > P4 > P2

thermal efficiency formula is 1-Qin/Qout, that one is for the next question (arrange by basis of thermal efficiency)
Looks right. What is the problem?

AM
 
Andrew Mason said:
Looks right. What is the problem?

AM

I don't know..masteringphysics said it's wrong :(
 

Similar threads

Finding exhaust temp in heat engine problem (entropy)
  • · Replies 1 ·
Replies
1
Views
6K
Thermal Efficiency of a Heat Engine based on pV-diagram
  • · Replies 23 ·
Replies
23
Views
12K
Waterfall plot of an PMSM
  • · Replies 1 ·
Replies
1
Views
1K
Thermodynamics of a Single-Component Ideal Gas
  • · Replies 1 ·
Replies
1
Views
2K
Calculating Heat Engine Efficiency: What is the Energy Input?
  • · Replies 2 ·
Replies
2
Views
2K
What is the power of a car engine?
  • · Replies 6 ·
Replies
6
Views
2K
How to calculate the efficiency of a fuel engine
  • · Replies 2 ·
Replies
2
Views
3K
Heat Exchange and Efficiency in a Fridge
  • · Replies 10 ·
Replies
10
Views
3K
Driving force over time to produce acceleration (graph)
  • · Replies 6 ·
Replies
6
Views
3K
How to Calculate Steam Engine Efficiency and Water Usage in a Power Plant
  • · Replies 18 ·
Replies
18
Views
9K