* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Potoourii of Interia Demos - Otterbein Neutrino Research Group
Angular momentum operator wikipedia , lookup
Fictitious force wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Classical mechanics wikipedia , lookup
Center of mass wikipedia , lookup
Centrifugal force wikipedia , lookup
Work (physics) wikipedia , lookup
Jerk (physics) wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Moment of inertia wikipedia , lookup
Relativistic angular momentum wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Equations of motion wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Hunting oscillation wikipedia , lookup
Classical central-force problem wikipedia , lookup
Seismometer wikipedia , lookup
Centripetal force wikipedia , lookup
Interia Demo’s 1. Mass on a rod/Balancing Stick 2. Water on a Tray 3. Mass on a String 4. Eggs Over Easy 5. Coins on a Coat Hanger 6. Toilet Paper Jerk 7. Ken & Barbie 8. Chalk on a Hoop 9. Apple Slices 10. Croquet Balls on Head 11. Tablecloth 12. Egg Spin 13. Bike Tire 14. Roto-rider 15. Inertia Video 1. Mass on a rod/Balancing Stick http://www.exploratorium.edu/snacks/balancing_stick/index.html The dowel rotates more slowly when the mass is at the top, allowing you more time to adjust and maintain balance. When the mass is at the bottom, the stick has less rotational inertia and tips more quickly. The farther away the mass is located from the axis of rotation (such as in your hand), the greater the rotational inertia and the slower the stick turns. An object with a large mass is said to have a great deal of inertia. Just as it is hard to change the motion of an object that has a large inertia, it is hard to change the rotational motion of an object with a large rotational inertia. You can feel the change in inertia when you do the following experiment. Grab the end of the dowel that's near the clay. Hold the dowel vertically, and rapidly move the dowel back and forth with the same motion you would use to cast a fishing line. Next, turn the dowel upside down, and hold it at the end that is farthest from the clay. Repeat the casting motion. Notice that it is much harder to move the dowel rapidly when the clay is near the top. The mass of the stick has not changed, but the distribution of the mass of the stick with respect to your hand has changed. The rotational inertia depends on the distribution of the mass of the stick. 2. Water on a Tray http://www.stevespanglerscience.com/experiment/00000145 This demo is a slight modification of the classic swinging pail of water demo. The picture shows the construction of the "spinning platform." The base is made from a square piece of Plexiglass measuring approximately 12 inches. Drill holes in all four corners large enough to accommodate a piece of rope. Attach the ropes to each corner of the platform and join them together in a knot about 2 feet above the platform. Now that all of the difficult work is finished, it's time to swing the tray and plastic cup (several plastic cups if you're feeling lucky) around in a complete circle without spilling the liquid or flinging the cup around the room. It's the tendency for the plastic cup and its contents to go in a straight line that allows it to seemingly defy gravity. The centripetal force provided by the tension in the cords is large enough to create enough friction to hold the plastic cup(s) in place. Here's a little advice... practice swinging the tray around without the cups in order to get the feel of a smooth, circular motion. Then add the cup filled half full with water. The liquid adds mass to the cup and helps to keep the cups in place. Some demonstrators even glue a thin piece of rubber to the bottom of the cup to give it a little gripping power (okay, friction) to help the cups stay in place. Shhhh! That's a little secret between you and me. How does it work? Here's the heavy-duty science for people who really care... According to Newton's First Law of Motion, objects in motion tend to remain in motion unless acted upon by an external force. In this case, Newton's Law requires the water to continue moving along a tangent to the circle. Thus a force is required to keep it always turning toward the center of the circle. The interpretation of this demonstration is potentially confusing when one considers that at the top of its arc, the water is accelerating downward because of the motion, but that the force of gravity is also downward. One can explain that F = ma is thus satisfied without the water leaving the bucket. This demonstration provides the opportunity to discuss non-inertial (accelerated) frames of reference and inertial (fictitious) forces (such as the centrifugal force 3. Mass on a String http://sirius.ucsc.edu/demoweb/cgi-bin/?mechan-statics-inertia Two equal weights suspended by threads, while two more threads hang below them with short rods for handles. When the handle is pulled down with a jerk, the lower thread breaks, but when it's pulled with an even force, the upper thread breaks. 4. Eggs Over Easy http://www.stevespanglerscience.com/experiment/egg-drop-inertia-trick We did it with a bent meter stick Materials: Small ball to practice with, if desired Cardboard tube Pie pan Raw eggs Water A large drinking glass Oh, you might need a few paper towels to clean up your practice mess! 5. Coins on a Coat Hanger http://www.wonderhowto.com/how-to-perform-easy-magic-trick-with-coathanger-and-coin-412841/ Same idea as the trick we showed but better This magic trick is really not so much a feat of illusion as a dizzying demonstration of physics. This video will show you how to do this easy trick with only a humble coin and coat hanger as props that will dazzle your audience for about 20 seconds with practice. 6. Toilet Paper Jerk Two rolls of toilet paper, one full and the other almost gone, are placed on a rod so that they are free to rotate. Inertia is discussed. Inertia is a measure of how difficult it is to get something to move. We use weight and mass to measure inertia. The heavier something is, the more inertia it has, and the harder it is to get it to move. A very sharp or fast blow applied to something with a lot of inertia is more likely to break it rather than move it. The same blow applied to something with less inertia is more likely to move it. It is very easy to rip off one or two squares of toilet paper with a quick jerk of one hand from a full roll without having it spin and unravel because of it's large inertia. However, it is almost impossible to do this with a roll that is almost gone. Because of it's low inertia, it is much easier to move. 7. Ken & Barbie Objective: to demonstrate Newton’s First Law of Motion (Inertia) students can see that objects at rest will stay at rest. Objects in motion will remain in motion unless a force is acting upon it. The motion of objects will continue in a straight line. Objects will eventually stop due to friction. This demonstration also covers Newton’s Second Law of Motion – Forces and Acceleration. When the “unbuckled” doll is launched, it accelerates – force causes acceleration. The force acting upon the “dolls” in the accident is the object the doll hits. Materials: 2 dolls 1 doll secured; 1 doll unsecured (duct tape) 1 skateboard Block/barrier to stop the board and eject one of the dolls Procedure: 1. Place the dolls on skateboard; secure one by taping or tying down. 2. Use a decline ramp (simply release the board) and place a barrier at the end of the route or push board on a level plane. 3. One doll should be launched to demonstrate acceleration and a net force acting on the “vehicle.” Conclusion: Two laws are observed. The board is in motion until acted upon by a net force. The dolls are at rest while on the board and Barbie stays at rest because she is buckled and Ken accelerates when acted upon by a net force (the barrier the board hits) and is propelled into the air. Ken accelerates while Barbie does not. To accelerate the mass it has to have a net force applied to it; the less mass the easier it is to accelerate. For example, a shopping cart full of groceries and a cart with just a gallon of milk. The lighter cart will accelerate at a faster rate than the other shopping cart. Science Terms: Inertia – An object at rest will remain at rest, an object in motion will remain in motion unless acted upon by a net force Friction – A resistance by having contact of solid to solid OR solid to air/water; eventually slowing an object down. Friction has three types on a surface: sliding, rolling, and static Acceleration – The rte in which velocity (speed together with the direction of the motion) is changing Net force – The combination of all forces acting on an object. For example: if you pull on an object at rest with 10 N (Newton) on a frictionless surface, then the net force will be 10 N and it is being acted upon by a “net force” of 10 N as it moves. Enrichment: A motorcycle accelerates from rest to 31 m/s in 10 seconds. Find the motorcycle’s average acceleration. Solve for acceleration: a = 31 m/s – 0 m/s 10 s 8. Chalk on a Hoop A piece of chalk is at rest on a very flexible hoop that has been balanced on top of a narrow neck bottle. When one tries to remove the hoop with a quick strike in the horizontal direction, the flexible hoop will change its shape to an oval one. As a result of the very low friction between the chalk and the hoop, the piece of chalk will fall straight into the bottle 9. Apple Slices Puncture a knife through an apple. Hold the knife so it is pointing down with the apple at the tip of the knife. Pound your fist on to the knife handle and the apple will appear to move up the knife. It is really a demonstration of inertia. The apple is at rest and wants to remain at rest. The knife moves downward Start Finish 10. Croquet Balls on Head /Mr. Potato Head Objective: This demonstration shows Newton’s First Law of Inertia. Objects at rest will stay at rest unless acted upon by a net force. The demonstration focuses on the object staying at rest, although there is a quick movement that occurs (turning your body). The interruption is brief, similar to a table cloth being yanked and the dishes remain. Materials: 1 coat hanger 2 potatoes or clay balls placed at each end Procedures: Prior to the demonstration, have students predict what will happen if you decide to “turn around” and face the other potato behind your head. Create camps of opinion and see which group’s prediction was correct. To create a potato head, open the hanger so it’s straight and then bend into a V-shape. Place the potato at each end; the weighted hanger will balance on your head. Have a potato in front of your face, and then quickly turn yourself around so that you will be facing the other potato. Conclusion: Students will see that the potatoes stayed at rest even though you were in motion. Friction is a factor that keeps or slows the hanger from moving. Newton’s first laws is observed when the potatoes stay at rest and you are in motion. Have students create or think of other ways to demonstrate this phenomenon. Science Terms: Inertia – An object will remain at rest OR an object in motion will remain in motion and move at a constant speed unless a force is applied Friction – A force that resists sliding between two touching surfaces or through air or water. Friction slows down an object. There are three types: static, sliding, and rolling Enrichment: Have students create or think of other ways to demonstrate this phenomenon. 11. Table Cloth The table setting rests on a silk tablecloth. Rapidly yanking the tablecloth out from under the setting pieces leaves the table setting unchanged. The plates are at rest and want to remain at rest. 12. Egg Spin Observation The hard-boiled egg will spin readily and stops soon after it is touched. But the fresh egg is difficult to get spinning and once it starts moving it is difficult to stop it from moving. Result Only the hard boiled egg spins readily since the mass inside it is solid and evenly distributed. In the case of the raw egg, the liquid within causes a drag effect that resists the spin initially and once the liquid is moving it resists coming back to the state of being motionless. The egg that spins readily and comes to a stop as soon as it is touched is the hard-boiled egg hence. 13. Bike Tire http://www.exploratorium.edu/snacks/bicycle_wheel_gyro/index.html A rotating bicycle wheel has angular momentum, which is a property involving the speed of rotation, the mass of the wheel, and how the mass is distributed. For example, most of a bicycle wheel's mass is concentrated along the wheel's rim, rather than at the center, and this causes a larger angular momentum at a given speed. Angular momentum is characterized by both size and direction. The bicycle wheel, you, and the chair comprise a system that obeys the principle of conservation of angular momentum. This means that any change in angular momentum within the system must be accompanied by an equal and opposite change, so the net effect is zero. Suppose you are now sitting on the stool with the bicycle wheel spinning. One way to change the angular momentum of the bicycle wheel is to change its direction. To do this, you must exert a twisting force, called a torque, on the wheel. The bicycle wheel will then exert an equal and opposite torque on you. (That's because for every action there is an equal and opposite reaction.) Thus, when you twist the bicycle wheel in space, the bicycle wheel will twist you the opposite way. If you are sitting on a low friction pivot, the twisting force of the bicycle wheel will cause you to turn. The change in angular momentum of the wheel is compensated for by your own change in angular momentum. The system as a whole ends up obeying the principle of conservation of angular momentum. Unfortunately, the gyroscopic precession of the wheel hanging from the rope is not explainable in as straightforward a manner as the rotating stool effect. However, the effect itself is well worth experiencing, even though its explanation is too difficult to undertake here. For more information, consult any college physics text under precession. 14. Roto-rider The sponge is forced by the cage into a circle. The water is unaffected by the cage (the cage does not apply a force to it) so it flies away from the sponge (in a straight line) Water