Simple Physics Questions Involving a A Bus and a Ball

This question has been bothering me lately, and with my non-existent knowledge of physics i can’t figure it out. Let’s say someone throws a ball up exactly 90 degrees, on a moving bus. Even though it’s a moving bus, instead of landing on someone in the back seat, it lands on the person who threw the ball, right? But if someone did the same thing on bicycle, the thrower wouldn’t be able to catch that ball because while the ball stayed in midair, he would’ve gone forward.
Why is this? Is it because it’s the bus is a closed space? If so, what difference would it make just because it’s a closed space?
Answers would be greatly appreciated. (Oh and if this question has been asked before, i apologize)

If your cyclist were in a vacuum, it would be the same as in the bus. It’s the wind resistance that slows the ball down, relative to the cyclist.

The only difference between the two situations would be wind resistance. On a bike, you will have to deal with wind resistance on the ball.

OK… i think i understand. See, i told you it was simple.(actually, i kinda feel stupid now)
But if the cyclist had a big window on the front of his bicycle, would that make a difference?

If he had anything that would provide still air (relative to the bike, rider, and ball) it would work just like the bus.

So the ball wouldn’t be left behind?
Hmm… Although that sounds reasonable, what bothers me is that the ball would actually be moving forward with the cyclist (with a window infront), instead of falling where it was thrown, as common sense would dictate. I don’t understand why the ball would move forward with you, even if there isn’t wind resistance. Bleh.

Picture yourself inside a room with no windows. You throw a ball up in the air, and it comes right down on your lap. Add a window and you find that you’re travelling in a railcar at a steady speed, not standing still.

Nothing changes. Everything inside the room (or on the bike or in the bus) is travelling at the same speed and will continue to travel at that speed unless something acts to slow it down. Throwing an object in the air (up/down) won’t affect the speed going forward.

Why don’t the bike riders clothes fall off and end up on the ground behind him? They are being carried forward along with the biker, just like the ball. The real question is why would the ball suddenly lose all that forward speed when you throw it up in the air?

From Newtons Laws: An object in motion will continue in motion unless acted upon by a force. Wind Resistance is that force that slows the ball down. Remove that force and there’s nothing to slow the ball down. It continues at the same speed as the bike.

Everything inside the bus has the same “momentum,” including the air. On a bike, the air is rushing by, hence the ball is “pushed” backwards.

A window in front of the bike might have the opposite effect by creating turbulence, and the ball might even be drawn forward.

On the bus, you, the ball, the bus and the atmosphere inside the bus are all moving, say, east at 20 mph. Propelling the ball upwards at 90º has no effect on its eastward travel. So it goes up and comes down in the same place relative to its local (all moving eastward at 20 mph) environment. What others have said about wind resistance is correct; I just thought that might help.

Telemark is dead on.

And a couple more facts.

  1. The ball thrown up and caught by a rider in a bus or bike (with something to stop the wind) would see the ball going straight up and down. Someone standing along the road would see the ball follow a curved path just like one you might see throwing a ball to another person. Except the person throwing the ball would move along with it, to catch the ball at its landing destination.

  2. The earth is not standing still. As viewed from some point off the planet, everyone’s balls would follow a curved arc, even if the ball appeared to be going straight up and down to the person with the ball.

Thanks to everyone that answered. I finally understand.

Sidenote: I knew i would feel stupid after hearing the answer. Which i do now. Darnit.

Someone quiet down those teenagers in the back, there. This is a physics lecture!

Take that one speedy soul traveling easterly at the same surface speed the earth has going west at that latitude, if they threw their ball straight up (from their moving frame of reference), it would appear to our hovering observer to go straight up and down, no?

OK, I’ll shut up.

Non-Native…that’s how we learn!
(The answers are right-on.)

  • Jinx

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