# Observer Watching a Ball Thrown Up on A Train [closed]

Let's suppose I'm on a train, moving with constant speed V1. At a time T1 I throw a ball up in the air, the ball do not accelerate but has constant velocity V2, and, in this hypotetical scenario, no force of gravity is experienced by the ball.
At a time T2 the ball reaches the roof of the train, which is located at a distance d on the z-axis, from the point I have thrown the ball.

A friend of mine, is watching on the platform. He sees the ball being thrown at T1, and then the train travelling a distance V1(T2-T1).

• Is it right to say he sees the ball moving along a diagonal path $\sqrt {d^2+(V_1(T_2-T_1))^2}$?
• What about the speed he sees the ball moving?

If there is any problem please comment below, and I will try to edit the question.

## closed as off-topic by Jon Custer, SchrodingersCat, sammy gerbil, heather, user259412Jun 7 '17 at 23:48

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• If the ball/train is on Earth and you throw it up in the air it will have acceleration downwards due to gravity. – JMac Jun 7 '17 at 9:58
• Can't I imagine an hypotetic situation whit a train moving and me thowring a ball without gravity? – Gabriele Scarlatti Jun 7 '17 at 10:01
• You can; but it's an extremely odd assumption to make for a "throwing the ball in the air" type problem. It wasn't clear that you were making that assumption, it seemed more likely to me that you just forgot about it. I suggest explicitly stating that in the question. – JMac Jun 7 '17 at 10:04
• Thank you very much, I appreciated a lot your comments! I tried to make it as clear as I can think of. If you have any other advice I'm happy to listen to them! – Gabriele Scarlatti Jun 7 '17 at 10:21
• The speed he sees the ball moving is V1 in the x(horizontal) direction and V2 in the y(vertical) direction or Vt = $\sqrt {V1^2 + V2^2}$ – Brad S Jun 7 '17 at 12:37