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Inflating Universe

What it shows:

According to present accepted theory the Universe came into existence some 17 billion years ago as a Big Bang and is currently expanding. You can model the expansion of space in two dimensions using a balloon.

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Shoot-n-Catch

Ball shot up from PASCO cart is caught by same; a puzzler to ponder if track is tilted and cart accelerates down (or decelerates up).

shoot-n-catch

Bow and Arrow

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

bow and arrow

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...

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Driven Damped Oscillator

Single air track glider, with and without variable frequency driver, variable damping, and oscilloscope position vs. time display.

What It Shows

With one end of the car attached via a spring to the end of the track and the other end of the car coupled (via a similar spring) to a driving motor, we can see how the car behaves when it is driven below, at, and above the resonance frequency. Markings on the motor help to show the phase relationships between the driver and car at different frequencies. A storage scope tracks the motion of the car (see Setting It Up...

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RC Time Constant

Charging and discharging of a 10µF capacitor with variable time constant.

What it shows:

The growth and decay of current in an RC circuit with a time constant chosen so that the charge and discharge is visible in real time.

How it works:

By choosing the values of resistance and capacitance, a time constant can be selected with a value in seconds. The time constant τ is given by

τ = RC

To obtain useful values, we chose three resistors 100K, 200K and 400K in series with a 10µF capacitor, giving time constants of...

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Color Mixing

What it shows:

All colors can be created from a combination of the three primary colors of red, green and blue. The secondary colors of cyan, magenta and yellow are created from a combination of two primaries, and white light is perceived from the combination of all three.

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Collapse of 55 Gallon Drum

Drum evacuated by vacuum pump; crushed by atmospheric bombardment.

What it shows:

With an air pressure of 105 Nm-2 at sea level, even a heavy duty oil drum will be crushed if it has nothing inside to balance the pressure.

How it works:

The screw cap on the drum is fitted with a vacuum pump connector. Simply turn on the pump and wait; it takes about 8 minutes to pump down, so you can carry on with what you were doing interrupted by various creaks and bangs as the drum's side walls begin to give....

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Bernoulli's Principle

What it shows

The relative velocities of two sides of a spinning ball to an oncoming wind creates a pressure difference and therefore a net force on the ball perpendicular to the air flow.

figure 1. Direction of motion of ball due to pressure difference

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