Power Transmition System Problem

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Discussion Overview

The discussion revolves around calculating the efficiency of a power transmission system in converting engine power to vehicle motion, specifically in the context of a sports car's performance metrics. Participants are exploring the relationship between rolling resistance, drag, and the overall power required at a constant speed.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant outlines the need to calculate power required to overcome both rolling resistance and drag at a constant speed.
  • Another participant confirms that power is the product of force and velocity, suggesting a focus on calculating drag.
  • A participant provides specific values for rolling resistance and drag at 140mph, along with the maximum power output of the car, and seeks guidance on calculating efficiency.
  • There is a question regarding whether the maximum power refers to the car or the engine, indicating a potential ambiguity in the problem statement.
  • A later post introduces a similar problem and questions whether potential and kinetic energy should be considered in the efficiency calculation.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the necessary steps to calculate efficiency, and multiple viewpoints regarding the inclusion of energy considerations remain unresolved.

Contextual Notes

There are missing assumptions regarding the definitions of power and efficiency in the context of the problem, and the discussion does not clarify the relationship between the engine power and the car's performance metrics.

shoaibshabba
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Hi Guys and Girls

I have a tutorial question that requires me to calculate the efficiency of the power transmittion system in coverting engine power to vehicle motion.

I have the rolling resistance at a specific speed and the required information to calculate the power required to overcome the drag.

I thouught to calculate the power require to overcome the rolling resistance and the drag but i am not sure where to go from here!

Any help would be great!
 
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You quite rightly state that the power required will balance the rolling resistance and the drag, at a constant speed. Power is force times velocity.

Do you know how to calculate the drag? If so where are you getting stuck?
 
Well the rolling resistance at 140mph is 200N and this results in an additional power required of 16.78hp.

The power required against the drag of the car at 140mph is 159.57hp.

The maximum power of the car is 190bhp at 7800rpm.

So how do i calculate the efficiency of the power transmittion system?
 
Either you're missing information, or you've not copied your question fully.

Does it say the maximum power of the car is 190bhp or the engine?
 
The exact question is -

A new sports car has the following published specifications and performance when fitted with a 1.8 litre, 16 valve, double overhead cam, turbocharged engine.

Maximum Power: 190bhp at 7800rpm
Maximum Speed: 140mph (level road,sea air)
Mass: 1200kg
Chassis Dimensions: 1.7 x 1.4 x 4.2 (widthxheightxlength)
Coefficient of drag for the vehicle is 0.34
Sea air density is 1.2 kg/m*3

If the rolling resistance of the vehicle at 140mph is 200N, estimate the efficiency of the power transmition system in converting engine power to vehicle motion.
 
Hi guys, i have a very similar problem to the one described here, could anyone provide insight into how to complete this?

Is there a need to take into account a gain in potential and kinetic energy of the car for efficiency?
 

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