Work done by a car engine up a slope

Click For Summary

Discussion Overview

The discussion revolves around the energy consumed by a car engine when it is used to maintain a stationary position on a slope with friction, particularly focusing on the mechanics of automatic and manual transmissions. Participants explore the implications of engine work in relation to the drivetrain and the effects of friction and heat.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the energy consumption of the car's motor when it is used to maintain a position on a slope, noting that while force times distance is zero, energy must still be consumed.
  • Another participant explains that in an automatic transmission, the motor produces mechanical energy that does work on the transmission fluid, which does not translate to work on the drive train due to the stationary output drive shaft.
  • A participant with a manual transmission shares personal experience of needing to rev the engine to move from a stop on a steep hill, indicating that work is done on the clutch plate.
  • There is a suggestion to use the handbrake to assist with hill starts, with a caution about the potential overheating of the clutch plate from excessive work.
  • One participant emphasizes the difficulty in calculating the power required to hold a car on a hill, suggesting that it is a complex issue.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics involved in maintaining a stationary position on a slope, with some focusing on the role of the transmission fluid and others on the clutch in manual transmissions. The discussion remains unresolved regarding the specifics of energy consumption and the calculations involved.

Contextual Notes

Participants acknowledge the complexity of the situation, including factors like friction, transmission types, and the limitations of calculating power requirements in this context.

kalamar20
Messages
12
Reaction score
0
Hello.
I've searched the internet hard but couldn't find anything about this so i decided to ask this to physicsforums.
If a car is up a slope with friction and it's stopping(balanced) by using the gas pedal, what is the energy consumed by the motor of the car? I know F.x is 0 in this situation but if I'm using the gas pedal, energy must be consumed right?
I'm starving for the answer, thank you for your interests!
 
Science news on Phys.org
Yes, mechanical energy is being produced by the motor and yes, that mechanical energy is not doing any work on the road.

In an automatic transmission there is a fluid coupling between the motor and the rest of the drive train. The energy that is produced by the motor is doing work on that fluid. But the fluid is not doing any work on the rest of the drive train (the output drive shaft is stationary).

So you have a net input of work into the transmission fluid. One can conclude the energy is being dissipated within the transmission fluid due to viscosity, heating that fluid up.
 
jbriggs444 said:
In an automatic transmission there is a fluid coupling between the motor and the rest of the drive train. The energy that is produced by the motor is doing work on that fluid. But the fluid is not doing any work on the rest of the drive train (the output drive shaft is stationary).


Or if you have a manual transmission like I do then your engine is doing work on the clutch plate... I deliver pizza in a hilly place. Sometimes I stop on a steep hill, then I have to rev it like mad to just get my car to move. I can smell the clutch plate from the work that has been done on it... lol, not good.
 
ModusPwnd said:
Or if you have a manual transmission like I do then your engine is doing work on the clutch plate... I deliver pizza in a hilly place. Sometimes I stop on a steep hill, then I have to rev it like mad to just get my car to move. I can smell the clutch plate from the work that has been done on it... lol, not good.

Have you considered using the handbrake to aid the hill start? If you're heating up the clutch to the point that you can smell it burning, that really isn't great for it...
 
Rev the engine and release the clutch with the hand brake on?

I use the hand brake when I stop of course, but when I release it my engine has to do work on the clutch plate. I don't hold it on the hill with the clutch if that is what you are asking. At least, not any longer than I have too! A second or less probably.
 
Last edited:
jbriggs444 said:
Yes, mechanical energy is being produced by the motor and yes, that mechanical energy is not doing any work on the road.

In an automatic transmission there is a fluid coupling between the motor and the rest of the drive train. The energy that is produced by the motor is doing work on that fluid. But the fluid is not doing any work on the rest of the drive train (the output drive shaft is stationary).

So you have a net input of work into the transmission fluid. One can conclude the energy is being dissipated within the transmission fluid due to viscosity, heating that fluid up.

ModusPwnd said:
Or if you have a manual transmission like I do then your engine is doing work on the clutch plate... I deliver pizza in a hilly place. Sometimes I stop on a steep hill, then I have to rev it like mad to just get my car to move. I can smell the clutch plate from the work that has been done on it... lol, not good.

Thank you very much for your answers I am glad to hear them!
 
...and I think it goes without saying that it is pretty much impossible to calculate how much power you need to use to hold the hill.
 

Similar threads

Undergrad Power delivered/Internal work done by a car's engine
  • · Replies 21 ·
Replies
21
Views
2K
Graduate Work done during adiabatic expansion on piston
  • · Replies 8 ·
Replies
8
Views
4K
Undergrad Sign convention on work done to a closed system containing gas
  • · Replies 5 ·
Replies
5
Views
3K
High School Is a Battery-Electric Vehicle Really More Efficient Than a Gas Car?
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Ideal working gas for a Stirling engine
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Is the energy output of an engine constant?
  • · Replies 31 ·
2
Replies
31
Views
6K
Undergrad Gas compression - does it double the energy?
  • · Replies 6 ·
Replies
6
Views
4K
Undergrad Is there any work done by static friction when accelerating a car?
  • · Replies 163 ·
6
Replies
163
Views
13K
Undergrad Does the work done by friction include the energy lost as heat in a system?
  • · Replies 2 ·
Replies
2
Views
3K
Work and Energy on a Slope - How Does a Block Move Up with Zero Net Work?
  • · Replies 3 ·
Replies
3
Views
2K