• Question: If you were standing in a train going at the speed of a bullet, and you fired a bullet, what would appear to happen to it, from your position within the train?

    Asked by ben1729 to Alan, Caspar, Diana, Murray, Sarah on 16 Mar 2011 in Categories: .
    • Photo: Caspar Addyman

      Caspar Addyman answered on 14 Mar 2011:

      Everyone would start screaming

    • Photo: Sarah Thomas

      Sarah Thomas answered on 14 Mar 2011:

      Err… what? Which direction do you fire it? The same direction as the train or opposite? I guess from your perspective, the bullet would travel normally because you and the bullet are both on the train. But if you were looking at it from outside the train, I guess it might look like the bullet isn’t moving? Or maybe it would look like it’s falling because of gravity?

      Phew! That’s a tough one!

    • Photo: Diana Drennan

      Diana Drennan answered on 14 Mar 2011:

      Relative to you, if you shoot forward or backward, it would still move at the speed of a bullet. But, and here’s the cool thing, if you shoot backwards, then to someone standing still looking at the train the bullet would appear to just drop to the ground !

    • Photo: Alan Winfield

      Alan Winfield answered on 16 Mar 2011:

      Nothing, Ben – the bullet would still appear to you to shoot out of the gun with the speed of a bullet. The reason is that you and the person with the gun are all travelling at the same speed – you are all in the same frame of reference – so the bullet will leave the barrel of the gun at bullet speed – relative to the train moving. The fact that the train is travelling at the speed of the bullet will only have an effect if you are looking from outside the train. So, imagine that you’re on the platform of the station and the train whizzes past at the same time as someone shoots the gun – pointing to the back of the train. If you could see the bullet through the windows of the train it would appear to the standing still – relative to you.

Comments

  • Photo: ben1729

    ben1729 commented on :

    I meant forwards, but ok, thanks!

    • Photo: Caspar

      Caspar commented on :

      Albert EInstein invented Special Relativity by thinking about a problem a bit like this. Namely what would happen if you shone a torch forward or backward on a train travelling at half the speed of light. The speed of light is constant everywhere in the universe so both you and someone on the platform would see the light moving at lightspeed.which is very different from what happens with the bullet.