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Bungee Jumping Barney

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...

What it shows:

When a magnetic field is applied perpendicular to a conductor carrying current, a potential difference is observed between points on opposite sides of the conductor. This happens because the magnetic field deflects the moving electrons (Lorentz force) to the edge of the conductor and the altered charge distribution generates a transverse electric field.

How it works:

The conductor is a small bar (11mm × 2mm × 2mm) of germanium (p-type?). Current (18 mA) is made to flow down the length of the bar by a 3 volt potential...

What it shows:

The photoemission of electrons from a metal surface depends on the energy of the incident radiation and not on its intensity. Knowing the energy of the emitted photoelectrons and the frequency of the incident light, you can calculate a value for Planck's constant h.

How it works:

Using a mercury source, we have at our disposal three very bright visible lines, in the blue, green and yellow (doublet), and a rich selection of ultra-violet. Our main source is a Phillips Lifeguard 1000W street lamp with its outer (uv...

The Surface Treatment of Glass

What it shows:

The strength of a material in tension or compression will be affected by discontinuities in its surface structure. This can be demonstrated for glass using microscope slides, and the comparison of failure stress before and after the removal of surface scratches.

How it works:

The slide rests between two custom built test beds (figure 1), the upper bed supporting the load. We use slotted 1kg and 0.5kg masses placed carefully in their holder, and allowing a short time between additions. We find the breaking...

Foucault Pendulum Model

What it shows:

A "working model" of a Foucault pendulum to show how its oscillations appear to change due to the rotation of "Earth" below it.

How it works:

The pendulum consists of 9-cm diameter brass ball suspended from a sturdy tripod which, in turn, sits on a heavy 3-ft diameter wooden disk. The disk represents the Earth with a projection of the northern hemisphere drawn on it. The suspension point of the pendulum is positioned over the North Pole. The entire apparatus sits on a ring bearing and the disk (Earth) can be rotated slowly by hand. While the plane of...

What it shows:

A pulse-modulated electromagnetic signal is simultaneously displayed in the time domain (on an oscilloscope) and in the frequency domain (on a spectrum analyzer). Using ∆n for the frequency spread (uncertainty in frequency) and ∆t for the duration of the pulse (uncertainty in the time domain), the frequency-time uncertainty relation is given by ¹

∆n ∆t ≥ ¹/_4π

By progressively shortening the length of time that the carrier signal is on, the inverse relation between pulse length and spectral-energy...

What It Shows

As shown in the drawing, the Mercator projection is a cylindrical map projection of the spherical globe. The meridians and parallels of latitude on the globe end up appearing as lines crossing at right angles in the projection. Areas on the globe far from the equator appear to be much larger on the projection. It's not trivial to visualize this projection and the intention of this demonstration is to shed some light on it (literally).

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What it shows:

Due to the rotation of the Earth, the plane of oscillation of a pendulum will rotate with respect to the surface beneath it. We expect a rotation of about 10˚/hr at our latitude of 42.˚

How it works:

Here the observer standing on the Earth resides in the reference frame, with the swinging pendulum oscillating in a rotating frame. From the pendulum's point of view, it keeps oscillating in the same plane, but the Earth spins below it. The deflection from its original plane...

Harvard Natural Sciences Lecture Demonstrations

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Demo Subjects

Key to Catalog Listings

214cc242b41c7c56d60acd8c0b8443ef

6a44dfa1d84d64f7cd2ee1fcd93b8644