Interactive Lecture Demonstrations                                         >Back
 Jonathan Bennett - bennett@ncssm.edu

Mechanical Demonstrations
Electrical Demonstrations

Mechanics

Lab Number Lab Title and Description
ILD 1 Investigating Motion with a Sonic Ranger 
In this activity, an ultrasonic motion detector ("Sonic Ranger") will be aimed at various objects. The SR can be used to determine the position, velocity and acceleration of an object, as a function of time. You will be asked to predict graphs of position, velocity and acceleration vs. time for various situations. Your graphs should be sketches; the shape of the graph (and whether the function is positive or negative) is the most important thing here. Make your graphs large so they are legible ! Scales are not needed on the axes, but labels are. All graphs for a given situation must use the SAME TIME SCALE.
ILD 2 Basketball Bounce
In this activity, a basketball will be held directly underneath a Sonic Ranger and then dropped onto the floor. The Sonic Ranger will create a position versus time graph for the basketball.
ILD 3 Howitzer
In this activity, a cannon ("Howitzer") will fire a cannonball horizontally off the edge of a table. The goal of this activity is to determine the speed with which the cannonball left the cannon (i.e. the muzzle velocity of the gun).
ILD 4 Howitzer II
The Howitzer returns – this time aimed at an upward launch angle of 30 degrees above horizontal. Also, rather than hitting the floor, the cannonball will be launched from one end of a table and will hit the tabletop somewhere at the other end of the table.
ILD 5 Force Diagrams
Force diagrams (sometimes called free body diagrams) are the key to solving problems involving Newton's Laws. A good force diagram will help you visualize the forces that act on an object and will also help you determine the net force on the object.
ILD 6

Atwood's Machine
An "Atwood's machine" consists of two objects connected by a string that runs over a pulley. In the beginning of this demonstration, one of the objects will be hanging in the air by the string; the other object will be sitting on a box. The mass of the hanging object is 0.6 kg, the mass of the object on the box is 1 kg.
ILD 7 Truck Parked on a Hill
In this demonstration, a block ("truck") is "parked" (i.e. is in equilibrium and is not moving) on a hill. A real truck would be held from sliding down the hill by the force of static friction of the road surface on the wheels. Our truck, though, is stopped from sliding by a barrier placed downhill of the truck. The angle of the hill is 37 degrees above horizontal. The mass of the truck is 435 grams.
ILD 8 Toy Airplane
In this demonstration, a toy airplane hanging from a string will move in a horizontal circle at a constant speed. By measuring the period and radius of the airplane's motion, we will be able to calculate the angle that the string should make with the vertical, and compare our calculated angle with the angle we measure directly.
ILD 9 Bucket of Water
A student will whirl a bucket of water in a vertical circle. The student will slowly decrease the speed of the bucket, until the water just barely stays in contact with the bucket. You will measure the period of revolution of the bucket of water for that situation and compare with the period you predict based on a force diagram analysis.
ILD 10 Merry Go Round
The Merry Go Round in this demonstration consists of a rotating stool on which a student will sit. The student will hold the center of a long stick and will rotate at a constant angular speed so that the stick moves in a horizontal circle. Horizontal accelerometers are attached to the stick with their centers at positions 45 cm and 90 cm from the center of the stick.
ILD 11 Bouncing Clay and Basketball
In this demonstration, we will compare two collisions. In one collision, a piece of clay will be dropped onto a scale and will stick to the scale. In the second collision, a basketball (that has the same mass as the clay) will be dropped from the same height as the clay onto the scale, and will bounce off the scale. The scale is interfaced to a computer. The scale measures the amount of force exerted on it by whatever comes into contact with it. The computer will plot a graph of that force vs. time.
ILD 12 Kinetic and Gravitational Energy
In this demonstration, a ball will roll down a curved ramp that sits on a tabletop. The ball will start from rest and will be moving horizontally when it gets to the bottom of the ramp. Once the ball leaves the ramp, it will undergo projectile motion until it hits the ground.
ILD 13 Ballpoint Pen Launcher
ILD 14 Rotating Board
A small ball sits on a stand at the end of the board. A small cup sits at some distance closer to the hinge. The board is lifted to an arbitrary angle q and then released. The purpose of this problem is to show that the vertical acceleration of the end of the board can exceed g, so that the ball can lose contact with the end of the board. If the cup is properly placed, the ball will fall into the cup.
ILD 15 Yo-yo- Torque
In this demonstration, we will study the torques created on the yo-yo by the string as it pulls on the central rod.
ILD 16 Yo-yo- Rotational Acceleration
In this demonstration, we will apply Newton's Second Law to both the translational and the rotational motion of a yo-yo. The yo-yo will be released from rest at a height of about 1 meter above the floor. As the yo-yo unwinds, its center of mass will accelerate downward. At the same time, the yo-yo will also have a rotational acceleration.
ILD 17 Mass on Spring
In this demonstration, a mass hangs from a spring. When the mass is pulled away from its equilibrium position and released, it will oscillate up and down in simple harmonic motion, because the net force on the mass is proportional to (and opposite to) the displacement from equilibrium. We will investigate the position, velocity, acceleration and force as a function of time for the oscillating mass, and compare the maximum values of these quantities to those calculated using the measured amplitude and period of the motion. We will use a sonic ranger to determine the position, velocity and acceleration of the mass, and a force sensor to measure the force of the spring on the mass.
ILD 18 Standing Waves on a String
We will create a standing wave on a stretched string, by vibrating the string up and down with a mechanical oscillator. This will be a transverse wave, since the motion of the string will be up and down, whereas the wave crests will travel left to right (or vice versa) on the string.
ILD 19 Ballistic Pendulum
In this demonstration a bowling ball and a sandbag hang side by side. Both objects can swing like pendulums. The sandbag will be drawn back so that it is a height hi above the bowling ball, and will then be allowed to swing to hit the bowling ball. Both objects will then swing together to some final height hf . The bowling ball is a ballistic pendulum, a device that is often used to measure the speeds of bullets by measuring the height to which the pendulum swings when hit by a bullet. Here, we will use the ballistic pendulum to determine what the speed of the sandbag was just before it hit the bowling ball. We will then compare our answer with the speed predicted using conservation of energy for the sandbag as it swings downward.

Electrical

Lab Number Lab Title and Description
ILD 1 Charged Balloons and Coulomb's Law
A balloon, hanging from a thread, will be charged by rubbing it with rabbit fur (one of the most electropositive substances known – this means that rabbit fur becomes positively charged by losing electrons to almost any object that you rub with it). A second balloon will be rubbed with rabbit fur and brought near the first one. The two balloons will repel each other due to the Coulomb (electrostatic) force of each on the other.
ILD 2 Oscilloscope
Refer to section 15.9 of Serway and Faughn for a description of how an oscilloscope works.
ILD 3 Van de Graaf Generator
In this activity, we will use a Van de Graaf generator to explore properties of conducting objects in the presence of electric fields. Refer to section 15.8 of Serway and Faughn for a diagram and description of how a Van de Graaf works.
ILD 4 Temperature of a Light Bulb Filament
The purpose of this activity is to decide whether a light bulb filament obey's Ohm's Law, and to determine the temperature of the filament.
ILD 5 Circuits with Two Light Bulbs
This demonstration involves two light bulbs: a 25 Watt bulb and a 40 Watt one. Recall that the bulb wattage is the amount of electric power that the bulb consumes. By definition, the electric power consumed by any device is P = IDV, where I is the current through the device and DV is the voltage difference between the two ends of the device. Using the definition of resistance, we can find two other formulas for electric power (only valid for resistors): P = I2R and P = (DV)2/ R.
ILD 6 Circuits with Three Resistors
In this activity, you will predict the current and voltage difference for each of three different resistors in a circuit connected to a battery. You will make your predictions using two different methods. You will then compare your predictions with the values of current and voltage difference measured directly using a digital multimeter.
ILD 7 Magnetic Forces on Currents
The purpose of this activity is for you to practice applying the Second Right Hand Rule (sometimes called the Palm-Push Rule). That rule tells the direction of the force that a magnetic field makes on a moving charge or current. The rule is: using your right hand, point your fingers along the direction of the magnetic field (think "fingers go with field"), and point your thumb in the direction of the velocity of the charge (i.e. the direction it is moving). Your palm will then be facing (think "palm pushes") in the direction of the force made by the field on a positive charge. If the charge is negative, the force on the charge is in the direction opposite to the way that your palm faces.
ILD 8 Electron's Charge-to-Mass Ratio
In this demonstration, a beam of electrons inside a partly evacuated glass sphere will enter a magnetic field that is perpendicular to the direction of the electrons' velocity. The magnetic field will be produced by two coils of wire arranged so that the separation of the coils is equal to their radius. This configuration of coils, called Helmholtz coils, produces a nearly constant magnetic field in the region between the coils.
ILD 9 Faraday's Law
In this demonstration, a solenoid will be connected to an alternating current source. A smaller coil (called the "pickup coil") will be put in the middle of the solenoid. An oscilloscope will be connected to the pickup coil. According to Faraday's Law, the changing flux through the pickup coil of the magnetic field made by the solenoid will cause an induced emf in the pickup coil. We will use Faraday's Law to predict the magnitude of the induced emf, then measure the induced emf with the oscilloscope and compare with our prediction. The diagram below shows the setup.
ILD 10 Lenz's Law
In this activity, you will push and pull a bar magnet in and out of a coil of wire, thereby changing the magnetic flux through the coil. According to Faraday's Law, an emf (and therefore a current) will be induced in the coil. According to Lenz's Law, the magnetic field produced by the induced current will always oppose the change in magnetic flux that caused the induced current. By measuring the directions of the induced currents in the coil with a galvanometer, you will test Lenz's Law. 
ILD 11 Radiometer
A radiometer is a pinwheel with paddles that are painted either black or white. All of the white sides face in one direction, all of the black sides face in the other direction. The pinwheel sits inside an evacuated glass bulb. When light shines on the radiometer, the pinwheel rotates due to the force of the light hitting the paddles.
ILD 12 Prisms
In this demonstration, we will predict and then observe the paths of light beams sent through prisms of various shapes.