Why cats land on their feet: and 76 other physical paradoxes and puzzles

Fun with physical paradoxes, puzzles, and problems. Introduction ; Background ; Sources

Outer space paradoxes. A helium balloon in a space shuttle ; Space navigation without jets ; A paradox with a comet ; Speeding up causes a slowdown

Paradoxes with spinning water. A puzzle with a floating cork ; Parabolic mirrors and two kitchen puzzles ; A cold parabolic dish ; Boating on a slope ; Navigating with no engine or sails ; The icebergs

Floating and diving paradoxes. A bathtub on wheels ; The tub problem : in more depth ; How to lose weight in a fraction of a second ; An underwater balloon ; A scuba puzzle ; A weight puzzle

Flows and jets. Bernoulli's law and water guns ; Sucking on a straw and the irreversibility of time ; Bernoulli's law and moving around in a space shuttle ; A sprinkler puzzle ; Ejecting water fast but with zero speed? ; A pouring water puzzle ; A stirring paradox ; An inkjet printer question ; A vorticity paradox

Moving experiences : bikes, gymnastics, rockets. How do swings work? ; The rising energy cost ; A gymnast doing giants and a hamster in a wheel ; Controlling a car on ice ; How does a biker turn? ; Speeding up by leaning ; Can one gain speed on a bike by body motion only? ; Gaining weight on a motorbike ; Feeling the square in mv²/2 through the bike pedals ; A paradox with rockets ; A coffee rocket ; Throwing a ball from a moving car

Paradoxes with the Coriolis Force. What is the Coriolis Force? ; Feeling Coriolis in a Boeing 747 ; Down the drain with Coriolis ; High pressure and good weather ; What causes trade winds?

Centrifugal paradoxes. What's cheaper : flying west or east? ; A Coriolis paradox ; An amazing inverted pendulum : what holds it up? ; Antigravity molasses ; The "proof" that the sling cannot work ; A David-Goliath problem ; Water in a pipe ; Which tension is greater? ; Slithering ropes in weightlessness

Gyroscopic paradoxes. How does the spinning top defy gravity? ; Gyroscopes in bikes ; A rolling coin ; Staying on a slippery dome ; Finding north with a gyroscope

Some hot stuff and cool things. Can heat pass from a colder to a hotter object? ; A bike pump and molecular ping-pong ; A bike pump as a heat pump ; Heating a room in winter ; Freezing things with a bike tire

Two perpetual motion machines. Perpetual motion by capillarity ; An elliptical mirror perpetuum mobile

Sailing and gliding. Shooting cherry pits and sailing ; Sailing straight into the wind ; Biking against the wind ; Soaring without updrafts ; Danger of the horizontal shear wind

The flipping cat and the spinning earth. How do cats flip to land on their feet? ; Can trade winds slow earth's rotation?

Miscellaneous. How to open a wine bottle with a book / "It's alive!" ; Falling faster than g : a falling chain "sucked in" by the floor ; A man in a boat with drag ; A "phantom" boat : no wake and no drag ; A constant-G roller coaster ; Shooting at a cart ; Computing the square root of 2 with a shoe

Appendix. Newton's laws ; Kinetic energy, potential energy, work ; Center of mass ; Linear momentum ; The torque ; Angular momentum ; Angular velocity, centripetal acceleration ; Centrifugal and centripetal forces ; Coriolis, centrifugal, and complex exponentials ; The fundamental theorem of calculus.