photo credit: Richard Heeps Photography

How Things Work: Front and Rear Bicycle Brakes

The car in this photo (hi-res version) is "doing a wheelie." Note the big racing slicks on the rear wheels--the force of friction that the road exerts on the rear tires creates a torque that rotates the front end of the car upwards. The same effect limits the effectiveness of the rear brakes; in this case the torque rotates the rear of the bicycle upward and reduces the rear tire's contact with the road (see How Things Work: Front and Rear Bicycle Brakes by Lou Bloomfield).

(This feature was updated on June 26, 2011.)

Login to Comment on this Item

Cold Metal

Visit Cold Metal for an Exploratorium activity on the science of heat. You'll make observations with your sense of touch and then interpret them.

To learn more, visit Thermal Conductivity, part of Phun Physics from the University of Virginia.

Advanced Search

Browse Physics To Go by Topic.

image credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF; image source.

Spectra

This image (hi-res version) shows sunlight spread out according to its color like the text in a page of a book (moving from left to right across the page, and then dropping down to the next line). The many dark vertical strips are absorption lines in the sun's visible spectrum. These lines are produced by atoms in the outer part of the sun, which absorb energy selectively. To find out more, see Atomic Absorption and Emission Spectra.

Analysis of these lines determines the chemical composition of a star. To learn more, visit Spectra.

(This feature was updated on April 26, 2014.)

Eames Office: Powers of Ten

To see the universe at different scales, from the most distant galaxies all the way down to subatomic particles, visit these sites:  
   Secret Universe: The Worlds Within by Molecular Expressions
   Powers of Ten by Charles and Ray Eames.

(This feature was updated on 8/15/2016.)