Balls (and other thrown objects) in a moving car

[Salty25]

What I've always wanted to know is - when in a moving car (or bus etc), if you throw a ball up and down, why is it that the ball goes up and down as if one were standing still, when surely you would expect the ball to go right to the back of the car the moment you throw it? I suppose you could also ask additionally why it is that flies (and other flying insects) can fly in a car and bus without also going straight to the back?

 

[Robbo]

With the ball, it is because when you throw it up and down it also travels in the same direction and speed as the vehicle, this is because you were travelling at that velocity when you let go of it.
It is the conservation of momentum. When you held the ball it had momentum (mass x velocity), when you let go of it the momentum has to be conserved, so it will continue to travel at the same velocity (since its mass has not changed). When you chuck it up you are superimposing a vertical movement onto it also.

With the fly it must be due to the air trapped within the vehicle. Smash your front and rear windows of your car to get rid of it.

 

[dig deep]

Now, if U put the pedal to the metal

and do the ball stunt

then the Ball would go backwards

as long as U accelerate

Like shooting a gun in a moving plane

If U don´t acc then the bullet doesn´t know that it is flying in a plane

 

[Salty25]

Thanks, I thought it had something to do with velocity, but I never bothered to ask anyone up to now (I've wondered this since my teens but never got around to asking why!).

Rob - I like your suggestion of how to get rid of a fly!

 

[Robbo]

We did momentum in O levels maths, (26 yrs ago for me).
I knew it was conservation of momentum, but must admit I did have to have a quick google to remind myself what it was.