90. Non-Newtonian Fluids

Corn starch and water are mixed in a plate to produce a goopy mixture that can be scooped up and dribbled with a spoon. Inviting the students to look closer, the professor suddenly slams his or her fist down on the mixture, causing the students to jerk back - but the mixture doesn't splatter; it momentarily becomes rock hard when acted on by a large force. Another type of behavior is demonstrated by dragging a spoon rapidly through the mixture to cause a ripping action.

Also available is "silly putty" which is hard and elastic under large forces but flows under small forces. Mold it into a ball and bounce it, and then leave on the lecture table; in ten or twenty minutes it will flow out under gravity.