Requiring little or no skill and the aid of a carpenter's square, one shot sinks two balls into the pockets.

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Currently we provide two different versions of this experiment. One version uses balls rolling down a long, inclined track (roughly 2 meters), and the other version uses balls that swing on a pendulum.

Track

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Same as previous except that mass ratio of balls is 1:3 (softball:basketball) leaving basketball dead and softball four times the height.

A tennis ball/basketball combination is dropped to the floor ... the tennis ball theoretically bounces to nine times the original drop height.

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What it shows:

Demonstration of elastic collisions between metal balls to show conservation of momentum and energy.

How it works:

Newton's Cradle (less affectionately known as Newton's Balls) consists of six rigid balls hanging in a row with bifilar suspension. The balls hang so that they just barely touch their neighbor.

Various initial conditions can be employed. A single ball displaced will collide with the remaining four, sending the ball at the far end off. Same idea for two or three balls. Four balls, and only the first two will stop; the center two...

What it shows:

Using conservation of energy, calculate the height from which Barney must jump so that his head just barely kisses the floor at the bottom of his bungee cord jump. Then verify by experiment. Oops ... hate when that happens! It turns out that it's not so simple and there are important details that must be taken into account.

How it works:

Barney (the friendly pink dinosaur) is "sandbagged" (with a 5 kg weight, duct-taped around his waist) and suspended from the sky-hook by a 3.1 meter-long (unstretched) spring. The spring constant has been measured...

Use conservation of energy to predict the height the arrow will reach.

What it shows:

When the string of a bow and arrow is pulled from equilibrium, the elastic potential energy in the bow is converted to kinetic energy of the arrow when...

A toy car rolling down a loop-the-loop track demonstrates the minimum height it must start at to successfully negotiate the loop.

What it shows:

For an object to move in a vertical circle, its velocity must exceed a critical value vc=(Rg)^1/2, where R is the radius of the circle and g the acceleration due to gravity. This ensures that, at the top of the loop, the centripetal force balances the body's weight. This can be shown using a toy car on a looped track.

How it works:

The car is released from the top of a ramp and runs down a slope towards...

Faith in the conservation of energy is tested by taking the demonstrator's nose to task.

What it shows:

The principle of conservation of energy ensures that a pendulum released at a particular amplitude will not exceed that amplitude on the return swing. A lecturer's faith in their subject is put to the test using a 50lb (22.7kg) iron ball.

How it works:

Technique is very important here. The best method to employ is to stand with your back against the blackboard with your head also touching the board. This ensures that you don't lean forward after release....

What it shows:

Two cars have the same mass and same spring bumper. When given a push and allowed to collide with a wall, one car bounces off with only a small reduction in speed ("elastic" collison) whereas the other car comes nearly to a complere stop ("inelastic" collision).

How it works:

There are two impulse cars made of identical materials and have the same mass. The car that models an elastic collision has all its lead sinkers securely attached to the frame so that they can't move. In contrast, the car that models an inelastic collision has the lead sinkers...

A wound-up spring propels a toy truck.

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A falling weight propels a car forward.

What it shows:

Gravitational potential energy can be converted into mechanical kinetic energy.

How it works:

A Gravicar is a vehicle powered by gravitational potential energy that it stores in...

What it shows:

The speed with which you tug on a toilet roll determines whether a sheet breaks off, or the roll simply unravels.

How it works:

The force applied to the junction between the sheets of a toilet roll is proportional to the rate of change of momentum of your hand as you tug at the end. Thus a sharp tug (large ∆p) is sufficient to surpass the breaking stress of the perforated junction. A lesser tug however, below the breaking stress, will apply a torque to the roll itself; the ensuing rotation unravels the roll.

figure 1. Toilet roll...

The instructor breaks several boards with a swift blow of the hand.

What it shows:

The impulse momentum theorem is demonstrated in a most dramatic way by breaking several boards with the blow of your fist. You need not be a karate expert to show how the force of a well executed hammer-fist strike will easily break a stack of five to eight boards. The impulse is given by

impulse = F∆t = ∆mv

The point of the demonstration is: the greater the speed, the smaller ∆t will be and thus the greater the force.

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Single seat CO₂ powered rocket cars.

Photo by Rose Lincoln