Car, gas and total energy calculation

  • #1
jeanmarc69
4
0
Hi,

What I understood about the principle of conservation of energy: Et = Ep + Ec = constant.
For example: Et = 1/2mv^2 + mgh (h = height).

Consider a car moving at speed v.

For example: Et = 1/2mv^2 + E(gas + exhausts). Indeed, I include the exhausts, otherwise with the drop in the quantity of gas necessary to drive the car, there is an imbalance, therefore no conservation.

My question: What would be the algebra for E(gas + exhaust) in the context of Et?

Thank you for your answers.
 
Physics news on Phys.org
  • #2
Wow, it's hard for me to decode your post. What are ##E_p## and ##E_c##? What are you trying to calculate? Are you trying to add the chemical potential energy of gasoline into a total energy calculation for a car? If so, the chemical potential energy of the exhaust can be taken as zero. If you have a turbofan driving the car, then I suppose you could include the exit momentum of the exhaust in the energy equations, but otherwise it makes little sense to worry about the exhaust gasses from a car, IMO.
 
  • #3
jeanmarc69 said:
My question: What would be the algebra for E(gas + exhaust) in the context of Et?
The air, taken in through the air filter of a car, must be first accelerated to the speed of the car. The energy required would normally appear as part of the aerodynamic drag of the vehicle. The fuel in the tank of the car would appear to be part of the mass of the vehicle.

The nitrogen in the air would be heated before being released as exhaust. The oxygen would be combusted with fuel, to be exhausted as hot H2O and CO2.

The exhaust gasses of piston-engined aircraft were directed backwards to gain a few HP of forward thrust. That 'jet' effect would also be true for cars, but is not as important as it once was in military aircraft.
 
  • Like
Likes berkeman
  • #4
Your math makes little sense to me too, but please note a car moving at constant speed on flat ground is not a situation where energy is conserved: 100% of it is lost.
 

FAQ: Car, gas and total energy calculation

What is the formula to calculate the total energy consumption of a car?

The total energy consumption of a car can be calculated using the formula: Total Energy (E) = Fuel Consumption (FC) × Energy Content of the Fuel (EF). For gasoline, the energy content is typically around 34.2 MJ/L (megajoules per liter).

How do I calculate the fuel efficiency of my car in miles per gallon (MPG)?

To calculate fuel efficiency in MPG, use the formula: MPG = Distance Traveled (miles) / Fuel Consumed (gallons). For example, if you traveled 300 miles and consumed 10 gallons of gas, your fuel efficiency would be 30 MPG.

How can I estimate the cost of a road trip based on gas prices?

To estimate the cost of a road trip, first calculate the total distance of the trip and your car's fuel efficiency (MPG). Then, use the formula: Total Cost = (Total Distance / MPG) × Gas Price per Gallon. For example, if your trip is 500 miles, your car gets 25 MPG, and gas costs $3 per gallon, the cost would be (500 / 25) × 3 = $60.

What factors influence a car's fuel efficiency?

Several factors influence a car's fuel efficiency, including driving habits (e.g., aggressive driving, speeding), vehicle maintenance (e.g., tire pressure, engine condition), aerodynamic drag, weight of the vehicle, and environmental conditions (e.g., temperature, road conditions).

How can I improve my car's fuel efficiency?

To improve your car's fuel efficiency, consider the following tips: drive at a steady speed, avoid rapid acceleration and braking, maintain your vehicle regularly (e.g., oil changes, tire pressure), remove unnecessary weight, minimize idling, and use cruise control on highways. Additionally, driving at moderate speeds and using air conditioning sparingly can also help.

Similar threads

Back
Top