PIRA |
Physics Lecture Demonstration MECHANICS (1K) - Applications of Newton's Laws |
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PIRA |
Physics Lecture Demonstration MECHANICS (1K) - Applications of Newton's Laws |
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1K - Applications of Newton's Laws
10. Dynamic Torque |
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| DCS # | Demonstration | Abstract/Description |
| 1K10.10 | tipping block | Pull with a spring scale at various angles on the edge of a block. |
| 1K10.10 | tipping block | A large wooden block is tipped over with a spring scale. |
| 1K10.10 | tipping block | A spring scale is used to show the least force required to overturn a cube. |
| 1K10.11 | tipping blocks | Same as TPT 22(8),538. |
| 1K10.11 | tipping block | Show the force necessary to tip over trapezoidal and weighted rectangular blocks. The students are surprised to discover the force needed is not related to the position of the center of mass. |
| 1K10.20 | ladder against a wall | Set a model ladder against a box and move a weight up a rung at a time. |
| 1K10.20 | ladder against a wall | A model ladder is set against a box and a weight moved up a rung at a time. |
| 1K10.20 | forces on a ladder | A small model ladder is placed against a box. |
| 1K10.20 | ladder forces | A real ladder leans against the wall. Animation shows the forces as the ladder moves. |
| 1K10.25 | forces on a ladder - full scale | Mount a set of wheels at the top of a ladder, place some shoes at the bottom to decrease friction and climb the ladder until you fall down. |
| 1K10.25 | forces on a ladder - full scale | Wheels are attached to the top of a ladder and the bottom slides on the floor. Climb up the ladder and fall down. |
| 1K10.30 | walking the spool | Pull at various angles on the cord wrapped around the hub of a spool to move the spool forward or back. |
| 1K10.30 | walking the spool | Pull on the cord wrapped around the hub of a spool at various angles to make the spool move forward or back. |
| 1K10.30 | walking the spool | Pull on a cord wrapped around the axle of a large spool. The spool can be made to go forward or backward depending on the angle. |
| 1K10.30 | walking the spool | A string is pulled off the inner axis of a spool at different angles, changing the direction the spool rolls. |
| 1K10.30 | walking the spool | A string wound around the center of a spool is pulled at different angles causing the spool to change directions. Diagram and analysis. See TPT 2(3),139. |
| 1K10.30 | spool with wrapped ribbon | The sides of the spool are made of clear plexiglass |
| 1K10.31 | walking the spool x three | Three rolling spools where the outer discs ride on rails and the center section with the string is larger, smaller, and the same size as the outer discs allowing one to always pull horizontally. |
| 1K10.40 | pull the bike pedal | Lock the front wheel, remove the brake, add training wheels, and pull backwards on the pedal in the down position. |
| 1K10.40 | pull the bike pedal | Pulling backward on a pedal (in the down position) of a brakeless bike will cause the bike to go back unless the length of the pedal crank is increased. |
| 1K10.40 | pull the bike pedal | Pull backward on a pedal at its lowest point and the bike will move backward. |
| 1K10.41 | traction force roller | Pull on a string wrapped around the circumference of a cylinder on a roller cart. Pull on a yoke attached to the axle of the same cylinder on the roller cart. |
| 1K10.41 | traction force roller | A large pulley on a roller cart is drawn either by a string wrapped around the circumference or by a yoke attached to the axle. |
| 1K10.41 | traction force roller | A large pulley can be drawn by either pulling on the axle or on a string wrapped around the perimeter. Try each case while the pulley is resting on a roller cart. |
| 1K10.42 | extended traction force | Pull on a string wrapped around the circumference of a cylinder placed on an air track glider. |
| 1K10.42 | extended traction force | A string wound around a cylinder, hoop, and spool is pulled while the objects are on a roller cart and the reaction force direction is surprising. |
| 1K10.50 | rolling uphill | A disc with a nonuniform mass distribution is placed on an incline so it rolls uphill. |
| 1K10.50 | rolling uphill | A loaded disc is put on an inclined plane so it rolls uphill or rolls to the edge of the lecture bench and back. |
| 1K10.50 | rolling uphill | A large wood disc weighted on one side will roll uphill or to the edge of a table and back. |
| 1K10.50 | loaded disc | A loaded disc can roll up an incline. |
| 1K10.80 | teaching couples | Start with two index fingers rotating a meter stick about the center of mass, use it to go into couples. Read it. |
| 1K10.81 | free vector | A strong magnet on a counterbalanced cork always rotates about the center of mass no matter where the magnet is placed. |
| 1K10.82 | couples | An arrangement to apply equal forces to opposite sides of a pulley mounted on a dry ice supported steel bar. |
| 1K10.83 | air jet couple | Air from a balloon is released through two nozzles offset from the center of mass. The assembly is free to rotate on a block of dry ice. |
| 1K10.90 | saw-horse on teter-totter | Good luck trying to demonstrate this one. |
| DCS # | Demonstration | Abstract/Description |
| 1K20.05 | washboard friction model | |
| 1K20.10 | friction blocks - surface material | Pull a block with four different surfaces with a spring scale. |
| 1K20.10 | friction blocks - surface material | A set of blocks with different surfaces are pulled with a spring scale. |
| 1K20.10 | friction blocks | Pull blocks across the lecture bench with a spring scale. |
| 1K20.10 | surface dependence of friction | Place brass blocks on an incline with four surfaces: teflon, wood, sandpaper, and rubber. |
| 1K20.12 | friction blocks | Several ways to move a surface under a fixed block. |
| 1K20.13 | sliding friction machine | A spring scale is attached to an object on a rotating table. |
| 1K20.13 | friction blocks | A device includes both sliding surface and mounted spring scale. |
| 1K20.13 | friction blocks | A block is constructed with an built-in apparatus to measure coefficient of friction directly. |
| 1K20.13 | friction blocks | An apparatus pulls a block at a constant speed and measures the frictional force. Details in appendix, p.550. |
| 1K20.13 | friction blocks | A block rests on a turntable and the string goes to a dynamometer. |
| 1K20.15 | weight dependence of friction | Pull a friction block with a spring scale, add a second equal block to the first and repeat. |
| 1K20.15 | weight dependence of friction | Add mass to a board pulled along the table with a spring scale. |
| 1K20.16 | friction blocks | A loaded cart rolls down an incline and hits a barrier. The load continues sliding on a second incline until it stops. The mass on the slider is varied to show stopping distance independent of mass. |
| 1K20.17 | friction blocks | Two additional points relating to Geoffery Fox's "Stumpers" column TPT. 11, 288 (1973). |
| 1K20.20 | area dependence of friction | A friction block has a rectangular shape with one side twice as big as the other. One of the smaller sides is routed out to 1/5 the area. |
| 1K20.20 | friction blocks | Friction independent of area of contact - cut a block to form a prism whose cross section is an irregular polygon. |
| 1K20.20 | area dependence of friction | A 2X12 is pulled along the bench top while resting on either the narrow or wide face. |
| 1K20.30 | static vs. sliding friction | Use a spring scale and block to show that static friction is greater than sliding friction . |
| 1K20.30 | static vs. sliding friction | Show that static friction is greater than sliding friction with a spring scale and block. |
| 1K20.35 | angle of repose | An incline plane is lifted until a block begins to slide. |
| 1K20.35 | angle of repose | Using the familiar suspended incline block apparatus to examine normal and frictional forces in sliding up and down the plane. |
| 1K20.35 | angle of repose | An inclined plane is raised until a block starts to slide. |
| 1K20.37 | tire friction | The automobile tire is a misleading example of static and sliding friction. |
| 1K20.37 | tire skid equation | Motivated by being an expert witness, An approximate expression for sliding friction coefficient as a function of speed was developed from published tables. |
| 1K20.37 | angle of repose | A plastic small parts drawer on a sanded aluminum surface allows weight to be added easily. |
| 1K20.37 | angle of repose | Using the incline plane for various friction demos. |
| 1K20.38 | how dry friction really behaves | A note arguing that the main rules of thumb about friction are wrong and the less said about friction the better. |
| 1K20.38 | angle of repose | A tribometer with a meter stick mounted vertically 1 m from the hinge gives a reading of coefficient of friction directly. |
| 1K20.39 | angle of repose | Glass - glass angle of repose with oil and oil/water. |
| 1K20.39 | angle of repose | The standard inclined plane and blocks + an interesting towel on a glass tube demo. |
| 1K20.40 | front and rear brakes | A model car is rolled down an incline with either front or rear brakes locked. |
| 1K20.40 | front and rear brakes | Construction details for a model car in which pulling a pin applies front, rear, or both sets of brakes to a car rolling down an incline. |
| 1K20.40 | front and rear brakes | A car slides down an incline with either front or rear wheels locked. |
| 1K20.40 | front and rear brakes | A car rolls down an incline with either front or rear wheels locked. |
| 1K20.40 | front and rear brakes | A toy car is modified so either the front or rear brakes can be locked. Slide down the incline plane for each case. |
| 1K20.40 | stability of rolling car | A toy car slides down an incline with either front or rear wheels locked. |
| 1K20.42 | friction roller | A cylinder in a yoke can be rolled or locked and slid as it is pulled by a spring scale. |
| 1K20.42 | friction roller | A cylindrical roller is pulled or slid across the lecture bench with a spring scale. |
| 1K20.42 | friction roller | A cylinder is pulled along and perpendicular to its axis by a yoke with a spring scale. |
| 1K20.45 | frictional force rotator | This article shows how to rotate a friction vector to make its component in a given direction as small as desired. Everyday unconscious applications of this method are presented along with some new demonstration equipment. |
| 1K20.46 | cross friction | Push a block across the slope of an incline and the block will move with a straight line trajectory. Knock a coin across and it will move in a curved path but all stopping points will be in a straight line. |
| 1K20.55 | squeaky chalk | You don't have to break chalk to eliminate squeaking, only understand friction and hold the chalk accordingly. |
| 1K20.55 | angle of friction with pencil | Tilt a pencil until it slides along the table. |
| 1K20.60 | sliding chain | Hang a chain over the edge of the table until the weight of the chain makes it slide. |
| 1K20.70 | falling flask capstan | Attach a 4 liter r.b. flask at the other end of a ball on a string and drape the flask over a horizontal rod 4' high. Let go of the ball. |
| 1K20.70 | falling keys capstan | A short analysis of the falling key capstan. |
| 1K20.70 | falling keys capstan | Hang a set of keys from a string draped over a pencil and when the string is released, the keys don't hit the floor. |
| 1K20.71 | discussion of the capstan | Friction experiments with the cord wrapped around a cylinder. Discussion of the donkey engine and capstan with a digression on sea chanties. |
| 1K20.71 | capstan on a force table | Tap a hole in the center of a force table and insert a bolt to use as a capstan. |
| 1K20.71 | capstan | Theory of the capstan along with discussion of applications. |
| 1K20.71 | capstan | Show the frictional force vs. the number of turns around a rod. |
| 1K20.74 | friction pendulum | A ball is suspended by a loop of string over a slowly turning horizontal wooden bar. A large amplitude results. |
| 1K20.76 | going up a tree | Very clever device. Look it up as its hard to describe. |
| 1K20.80 | Snoek effect | If you don't know about the Snoek effect, don't ask me - I had to read up on it too. |
| 1K20.85 | WWII torpedo story | Friction caused dud torpedo in WWII. |
| 1K20.90 | air track friction | Show there is little friction on an air track. |
| 1K20.95 | teflon cookie sheet | Cut up a teflon coated cookie sheet for an inexpensive teflon surface. |
| 1K20.95 | teflon pulley | Teflon sheet bent around corner replaces a pulley. |
| 1K20.95 | Dylite beads | Dylite beads on a rimmed glass surface (window pane) provide a low friction surface. |
| DCS # | Demonstration | Abstract/Description |
| 1K30.10 | bed of nails | Lie down on a bed of 16d nails on 1" centers. |
| 1K30.10 | bed of nails | Lie down on a bed of 16d nails on 1" centers. |
| 1K30.10 | bed of nails | The instructor lies on a large board with nails at 1" centers. |
| 1K30.10 | bed of nails | Break a block on the chest of a person lying on a bed of nails. |
| 1K30.20 | pop the balloons | A disc with points on one side can be placed on balloons so either the points or flats rest on the balloons. |