Falling Faster Than g

A hinged board rotates under the force of gravity and the free end accelerates at a rate faster than g. This board is 1 meter long and starts at an initial angle of just under 35 degrees. A steel ball bearing sits on a golf tee about 2 cm above the end of the board.

For more information on this setup see http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa...

Thanks to Rob for letting us use the camera.

Category:

Education

Tags:

• rotational dynamics
• torque
• angular acceleration
• classical mechanics
• free fall paradox
• science
• demonstration
• 600 fps

[daimonionen]

So what? And whats "g"?

[NatSciDemos]

@daimonionen g is an object's weight divided by its mass.

[gwg68]

How large would you have to scale up this demonstration to show the effect the motion of the earth has on the free falling steel ball? Can it be done?

[NatSciDemos]

@gwg68 By VERY CAREFULLY releasing the ball in a controlled manner, you can measure its (very small) deflection when it's dropped from a height of three or four stories.

[Chasmodius]

Also, it would be nice to have a scale in the background, which would allow a frame-by-frame speed determination, as well as showing clearly what vertical distance is between the ball and cup both at the beginning and at the moment that the cup hits the table. Great, now I've got to get access to a high-speed camera so I can do this demonstration myself!

[NatSciDemos]

@Chasmodius yes a grid would help and we would have used one if we weren't so lazy. as you can see from the high speed footage the lens adds a bit of distortion, so the challenge would be to overcome that. if you do make your own (and we encourage you to) we found that a yogurt cup works well ;)

[gizmoguyar]

So, the center of mass of the board accelerates at G, and one end slower, and one end faster? Like if you spun a bike tire off a roof, one side would be traveling downwards faster than the other, but the tire as a whole would accelerate at G?

[omermallhi]

God I love science and waiting when religion can be scientifically proved

[lohse63]

it doesn't fall faster, the cup just falls shorter due to placement on the plank. try holding a finger tip under the ball, yes it falls straight down the cup moves because it sits on the plank

[1sword4you]

both of them fell slower than g. to actually reach the speed of g you must set the experiment in vacuum environment and to get faster than g you have to take to Jupiter or Sun or any other Cosmical object heavier than Earth

[girlfoxproduction]

they are falling at the same speed it is just the marble is higher and you put the cup under it

[animes25]

the ball is centimeters up the cup, so it haves to travel more distance

[mentox]

@daimonionen

G is the acceleration of an object due to gravity

[Surferdud50]

The ball remains a constant height above the cup, and the ball falls in a straight line. The vertical component of the cup's velocity of is therefore same as the ball's vertical velocity. Gravity at sea level is a vertical force. Therefore no object here is falling faster than g, it is just an optical illusion

[haakondahl]

The bearing (the ball) is the one thing we trust to move at its predicted rate. The center of mass of the beam falls at ALMOST g, but some of the work is transferred into rotation rather than downward movement, because the left end is hinged.The right end not only falls with the center of mass, but rotates clockwise around it. Yes, the cup moves downward faster than gravity pulls it. But only part of that is "falling". The rest is rotation.