# physics

• Nov 22nd 2012, 06:35 AM
Louisana1
physics
A person drops a ball in a train traveling along a straight, horizontal track at a constant velocity. What would the person in the train say about the horizontal forces acting on the ball?

a. There are no horizontal forces acting on the ball.
b. There is a fictitious (inertial) force acting forward.
c. There is a fictitious (inertial) force acting backward.
d. There is a centrifugal force.
• Nov 22nd 2012, 06:52 AM
skeeter
Re: physics
Quote:

Originally Posted by Louisana1
A person drops a ball in a train traveling along a straight, horizontal track at a constant velocity. What would the person in the train say about the horizontal forces acting on the ball?

a. There are no horizontal forces acting on the ball.
b. There is a fictitious (inertial) force acting forward.
c. There is a fictitious (inertial) force acting backward.
d. There is a centrifugal force.

what do you think, and why?
• Nov 22nd 2012, 06:53 AM
emakarov
Re: physics
Hmm, I can repeat my spiel about the "throwing force"... Recall the first and second Newton's laws and take into account that a train traveling at a constant velocity is an inertial reference frame, where the Newton's laws hold.
• Nov 22nd 2012, 09:15 AM
Louisana1
Re: physics
I would say that it moves forward
• Nov 22nd 2012, 09:27 AM
Louisana1
Re: physics
no force acting on it
• Nov 22nd 2012, 09:29 AM
skeeter
Re: physics
the person on the train would see the ball fall straight down from his frame of reference.
• Nov 22nd 2012, 09:41 AM
Louisana1
Re: physics
no force would be acting on it if a person on a train would see it, but really it would move forward?
• Nov 22nd 2012, 10:43 AM
emakarov
Re: physics
Quote:

Originally Posted by Louisana1
no force would be acting on it if a person on a train would see it, but really it would move forward?

You are right about the force. When you say "it would move forward," you mean with respect to which frame of reference: the train or the track?
• Dec 14th 2012, 07:58 AM
juanjuan
Re: physics
What would the person in the train say about the horizontal forces acting on the ball?
• Dec 14th 2012, 09:23 AM
ebaines
Re: physics
You might also ask what an observer on the ground would say about horizontal forces acting on the ball as it drop. He'd have the same answerto this as the observer on the train.
• Dec 15th 2012, 06:32 AM
puresoul
Re: physics
So is the correct answer (a) ??
• Dec 15th 2012, 06:55 AM
a tutor
Re: physics
Perhaps if the ball on the train dangles from a string and the string is cut it is more obvious to any confused students that there is no sideways force?

I read emakarov's Meowton post. I hope that one day I too am so confident that I'm respected that I can talk nonsense without being afraid that people will think I'm an idiot. :)
• Dec 15th 2012, 07:19 AM
puresoul
Re: physics
Quote:

Originally Posted by a tutor
Perhaps if the ball on the train dangles from a string and the string is cut it is more obvious to any confused students that there is no sideways force?

I read emakarov's Meowton post. I hope that one day I too am so confident that I'm respected that I can talk nonsense without being afraid that people will think I'm an idiot. :)

^^ Me too
It was funny..
• Dec 15th 2012, 10:45 AM
skeeter
Re: physics
Quote:

Originally Posted by puresoul
So is the correct answer (a) ??

yes