the horizontal speed of the pillow relative to the ground?

Question

In the cabin of a jetliner that cruises at 600 km/h, a pillow drops from an overhead rack into your lap below Since the jetliner is moving so fast, why doesn't the pillow slam into the rear of the compartment when it drops? What is the horizontal speed of the pillow relative to the ground? Relative to you inside the jetliner?

Answer 1

Hi,

Galileo was faced by similar queries and this is his response:

Shut yourself up with some friend in the main cabin below decks on some large ship, and have with you there some flies, butterflies, and other small flying animals. Have a large bowl of water with some fish in it; hang up a bottle that empties drop by drop into a wide vessel beneath it. With the ship standing still, observe carefully how the little animals fly with equal speed to all sides of the cabin. The fish swim indifferently in all directions; the drops fall into the vessel beneath; and, in throwing something to your friend, you need throw it no more strongly in one direction than another, the distances being equal; jumping with your feet together, you pass equal spaces in every direction. When you have observed all these things carefully (though there is no doubt that when the ship is standing still everything must happen in this way), have the ship proceed with any speed you like, so long as the motion is uniform and not fluctuating this way and that. You will discover not the least change in all the effects named, nor could you tell from any of them whether the ship was moving or standing still. In jumping, you will pass on the floor the same spaces as before, nor will you make larger jumps toward the stern than toward the prow even though the ship is moving quite rapidly, despite the fact that during the time that you are in the air the floor under you will be going in a direction opposite to your jump. In throwing something to your companion, you will need no more force to get it to him whether he is in the direction of the bow or the stern, with yourself situated opposite. The droplets will fall as before into the vessel beneath without dropping toward the stern, although while the drops are in the air the ship runs many spans. The fish in their water will swim toward the front of their bowl with no more effort than toward the back, and will go with equal ease to bait placed anywhere around the edges of the bowl. Finally the butterflies and flies will continue their flights indifferently toward every side, nor will it ever happen that they are concentrated toward the stern, as if tired out from keeping up with the course of the ship, from which they will have been separated during long intervals by keeping themselves in the air. And if smoke is made by burning some incense, it will be seen going up in the form of a little cloud, remaining still and moving no more toward one side than the other. The cause of all these correspondences of effects is the fact that the ship's motion is common to all the things contained in it, and to the air also. That is why I said you should be below decks; for if this took place above in the open air, which would not follow the course of the ship, more or less noticeable differences would be seen in some of the effects noted.

Although, this seems obvious to us now in its day it was quite startling. But it is the same for an Astronaut on a space walk. His craft appears stationary to him, although both he and it a traveling at great speed. So, we judge that something is moving only by its movement relative to us or some other object.

This, if you like, is Galilean relativity, we judge objects to be moving only if they are moving relative to our frame of reference.

Answer 2

Because the air speed is the same inside the jetliner! The pillow is moving 600km/h relative to the ground.... Relative to you, it is only moving vertically, not horizontally because you and the pillow are going the same speed.

Answer 3

The pillow only falls because the force became unbalanced. There's no horizontal force on the pillow, only the force of gravity down. Since it's moving along at a steady horizontal velocity it continues having that same horizontal velocity component. Orthogonal forces don't affect motion in the other direction. A bullit fired horizontally and a bullet dropped at the same time both hit the ground at the same time. Think vectors.

Answer 4

The plane, the pillow, and you are all traveling at the same speed. Anything that is in a plane will have the same horizontal motion as the plane; so the pillow, you, and the plane are all traveling at 600 km/h.

Answer 5

when the pillow is droped from the jet the pillow gets THE SAME VELOCITY AS THE JET I.E. 600KMPH
so it travels insame vertical line as the jet and in our lap
THIS ANSWER IS 100% CORRECT
relative to ground vel=600kmph
rel 2 jet=100kmph

Answer 6

a) 600km/h
b) 0km/h