Accelerated Reference Frames – 1G20.00

Weightlessness in Free Fall – Mass in Cup on Pole – 1G20.38

  • A long broomstick has a cup attached to the end.
  • Inside the cup are a ball and a weak spring.
  • When the ball hangs out of the cup the spring is too weak to pull it back in.
  • When the stick is raised up in the air and released gravity is instantly switched off.
  • In the absence of gravity (freefall) the weak spring has the ability to pull the all back into the cup.
  • This apparatus is also called Einstein’s Toy. It was designed by Eric Rogers of Princeton and presented to Einstein on his 76th birthday.

Location: Jacobs B122 – Shelf 284

Dropped Slinky – 1G20.45


  • Hold a slinky so some of it extends downward, and then drop it to show the contraction.

Location: Jacobs B122 – Shelf 163