# Need Physics help pls

• Nov 21st 2012, 07:44 AM
Louisana1
Need Physics help pls
A person drops a ball in train traveling along a straight, horizontal track at a constant velocity of 50 mph. An observer on the ground (that is, standing next to the tracks) would determine that the horizontal velocity of the ball during the fall is

a. zero
b. equal to 50 mph
c. increasing
d. decreasing
• Nov 21st 2012, 07:54 AM
grillage
Re: Need Physics help pls
A person would do very well to determine anything in that situation (Happy), but if you have to provide an answer then I would guess that an onlooker would see the ball travelling at the same speed as the train, although technically it would be slowing down very slightly.
• Nov 21st 2012, 09:12 AM
HallsofIvy
Re: Need Physics help pls
Quote:

Originally Posted by grillage
A person would do very well to determine anything in that situation (Happy), but if you have to provide an answer then I would guess that an onlooker would see the ball travelling at the same speed as the train, although technically it would be slowing down very slightly.

Why? Not because of air resistance because the air is moving with the train and so, horizontally, with the ball.
• Nov 21st 2012, 12:41 PM
grillage
Re: Need Physics help pls
Good point. So I guess that the answer will be b then.
• Nov 22nd 2012, 03:56 AM
topsquark
Re: Need Physics help pls
Rule of thumb: If a problem does not specifically mention air resistance, you can usually ignore it.

-Dan