1
$\begingroup$

Consider a car floating in a microgravity environment. Assuming the engine can still function (i.e. it is surrounded by normal atmosphere; fuel can still be pumped, etc.), in what ways (if any) will the car move when the accelerator is pressed?

There is air moving into the intake and out of the exhaust, will that cause a net acceleration forward?

Will air resistance with the wheels cause any sort of net acceleration?

Will the torque from the engine cause the car to rotate at all?

$\endgroup$

3 Answers 3

2
$\begingroup$

The movement would depend on several factors, such as wether the engine was transverse or longitudinal. However, the most pronounced motion would be some compound form of rotation. Most of the moving parts in a car rotate, so in the absence of gravity the rotation of parts of the car would generate counter rotations of the rest. If the car had a longitudinal engine, the rotation of the crankshaft and flywheel would cause a counter rotation of the body around a lengthways axis. The rotation of the driving wheels will cause a counter rotation of the body around a transverse axis. Switching on the windscreen wipers will cause an oscillation of the body. There would also be some longitudinal acceleration, not just from the exhaust but also from the radiator cooling fan, and the heater/air-conditioning fans which propel air rearwards.

$\endgroup$
2
$\begingroup$

in what ways (if any) will the car move when the accelerator is pressed?

For conservation of momentum, the momentum of the exhaust gases rearward out the tail pipe must be equal to and opposite to the momentum of the car forwards. So in theory the car can accelerate in the same manner as a rocket in space, though the thrust of a car due to its exhaust gases would likely be weak.

Hope this helps.

$\endgroup$
-1
$\begingroup$

In this case there is only one way to accelerate the car, The exhaust. We know from newton third law of motion that every action has an equal and opposite reaction.There are no roads so the wheels are useless.Wheels also work on the same concept of newton 3rd law.So when the air comes out of the exhaust it accelerates the car in the opposite direction.
If taking about other possible types of motion you may thing about Torque but it is not the case because the force is acting along the line of centre of mass and we know it will not create any type of torque but if we will change the angle of exhaust ejection it may create both translational and rotational motion. The other way to accelerate the car is to throw something out of the car and the car will accelerate.
Remember we are taking about very less acceleration. The exhaust cannot produce sufficient thrust to accelerate the car to , say 30 kmph. Even 1kmph is a difficult goal for the car. But you can increase the thrust by reducing the area of ejection nozzle and some other Thermodynamic processes but for now this was your answer.

$\endgroup$
1
  • $\begingroup$ Any amount of thrust will eventually achieve any velocity - it just depends on how long it acts for. Ion motors for instance produce very small thrust but act continuously for months to produce very high velocities. It is the acceleration that is small - not the final velocity $\endgroup$
    – Wreckless
    Feb 2 at 21:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.