A realistic model of the forces in the erector spinae muscles that support the back when bent over.
What it Shows:
This is an analysis of the tensions in muscles and forces on joints as an application of torques in static equilibrium situations. The muscles involved in supporting the human torso in a stooped position are realistically modeled, and the extraordinary large forces calculated and demonstrated.
How it Works:
When bending over into a stooped position, the principal muscles which support the back are the erector...
Conservation of angular momentum and the exponential increase in friction are what save the coffee mug from smashing into the floor. Use this entertaining demonstration to introduce either of those physics concepts.
How it works:
You need a pencil, a pen, a china cup (we use a china cup to add suspense and a threat of disaster), and about 1 meter of string. Tie one end of the string to the cup and the other to the pen. Hold the pencil in one hand and drape the string over it so the cup hangs down a few centimeters. Hold the pen with your other hand (arm...
Electricity is never created or destroyed, but only transferred. Rubbing fur and Teflon™ together transfers charge (electrons) from the fur to the Teflon, making the Teflon negatively charged. Conservation of charge requires the fur to become equally and oppositely charged as is demonstrated in this experiment to an accuracy of ≤1%.
How it works:
The difficulty in demonstrating charge conservation quantitatively lies in catching all the charge before it leaks away, the fur being the main problem. This is overcome...
It's impossible to magnetically levitate an object with static magnetic fields. However, it's posible to levitate a magnet with another hand-held magnet by taking advantage of eddy currents.
How it works:
A rectangular block of copper (6"×6"×2") is stacked on top of another one (6"×6"×1"). They are separated by 1" plastic spacers. A rectangular bar magnet (2"×2"×½") is placed in the space between them. When a second magnet is lowered from above, the two magnets attact each other. However, rather than "jumping up"...
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...
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.
A vacuum is drawn over a beaker of sliced cucumber covered in a clear dressing. The cucumber outgases, making bubbles. When the atmosphere is readmitted, the dressing is forced into the cucumber, rendering it translucent and seasoned.
A polycarbonate bell jar with a volume of about three liters is centered on the base, with attention to the seal. The vacuum pump tube ID is the same as the outlet tube OD, so attach by hand. Vacuum release by sliding the vinyl tube off of the outlet.
The vacuum pump is the oil-less variety, and is not bothered by water. The pump is...