1. Why won't the paper go into the bottle? In trying to push the paper into the bottle, you are aiming the air stream at the mouth of the soda bottle. The hair dryer pushes air into the bottle, filling it with air. In fact, the bottle is so full of air that there is room for nothing else - not even a little ball of paper. If you turn off the hair dryer or aim it away, the air can escape the bottle and there is room for the paper.
2. How did the penny disappear? We see objects because light rays reflect off them and into our eyes. But light bends each time it hits a substance of a different density. The light reflecting off the penny must pass through air, glass, and water (all with different densities) to get to your eye but the light bends so many times that by the time it gets to your eye, it looks like it's someplace it's not!
3. Why did the pepper "run away"? The pepper sprinkled on the water stays in place because the water is pulling on the pepper evenly in all directions. When the detergent comes into contact with the water in the center, it reduces the water's pulling action on the pepper and the pepper appears to run away from the detergent. But the water around the edges (untouched by the detergent) still has its pulling strength.
4. Why did the empty jar win? Initially, the water-filled jar moves down the ramp faster than the empty one. This happens because its weight is evenly distributed throughout its volume, thanks to the water inside it. The empty jar's weight is all in the glass perimeter so it doesn't roll quite as fast. But as the jars begin rolling on the flat surface, the greater weight of the full jar causes friction between the jar and the floor as well as friction between the water and the inside of the jar. The full jar slows down, allowing the lighter, empty jar to take the lead!
5. Why couldn't I get any water from the jar? When you drink from an open glass of water, air pressure allows the water to travel up the straw. When you reduce the pressure inside your mouth (by sucking on the straw), the surrounding air pressure pushes down on the water and forces the liquid up the straw. But when air pressure on the water is blocked (when you seal the jar lid), there is no air pressure to help push the water up your straw. The air canŐt get to the water to push on it, so it doesn't go up the straw. Regardless of how hard you suck, the water stays where it is!
6. Why did the quarters land at the same time? The quarters start from the same height off the ground and are the same mass and shape, so gravity and air resistance worked on them in exactly the same way. Even if an object is thrown straight out, it will fall to the ground in exactly the same amount of time as an identical object that is dropped - the acceleration toward the ground that the objects experience as a result of gravity causes them to hit at the same time.
Director of Outreach & Promotion NEWTON'S APPLE 172 4TH ST E SAINT PAUL MN 55101 e-mail:newtons.apple@umn.edu