# Does driving a car affect the Earth's rotational velocity

1. Nov 13, 2014

### shott92

hi guys
really odd question (no such things as a silly question)
but i was just thinking about this and well according to newtons every action has an equal and opposite reaction
well i know im talking fractions of a degree per millenia or there abouts i guess
but when i get in my car with a mass and accelerate (lets say east)
then does this actually have an impact on the rotational speed of the earth

cheers for the time and answers :D

2. Nov 13, 2014

### A.T.

Yes.

You cannot accelerate your car east for millennia. As soon you reach constant speed, you are giving all the momentum you are gaining back to air, which gives it back to the Earth. And when you stop the Earth has it's original amount of angular momentum again. All the different interactions average to zero over time. Only external bodies, like the Moon can exert a "permanent" torque that reduces the Earth's angular momentum over millennia.

If you want to slow down the Earth's rotation permanently, you have move closer to the equator and stay there.

Last edited: Nov 13, 2014
3. Nov 13, 2014

### shott92

pretty much as i thought, thanks
although i did over think it and figured that the forces would almost equal out due to usually when you drive to a location you drive back home (return trip) lol ... forgot about braking :/
but thanks for that picture too, made me smile :D

4. Nov 13, 2014

### A.T.

For north-south travel you have to return to the same latitude to restore the original Earth rotation.

You don't have to actually use the brakes. The air that slows you down transfers it's momentum the Earth, with some delay though.

5. Nov 14, 2014

### CWatters

Presumably using fuel will have converted some mass (that was originally below the earths surface) into gasses (mass above the earths surface). I guess that might change the rotational velocity of the planet even if the car returns home :-)