Thursday 14 January 1668/69

Up and to the office, where all the morning busy, and so home to dinner, where Goodgroome with us, and after dinner a song, and then to the office, where busy till night, and then home to work there with W. Hewer to get ready some Tangier papers against to-morrow, and so to supper and to bed.

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Terry Foreman  •  Link

The Royal Society today at Arundel House — from the Hooke Folio Online

/75/ Ian. 14. 1668/9. - the Curator shewed by two sorts of Expts. that the force in moving bodys is in a duplicate proportion to their celeritys, soe tht there is required a quadruple weight to double the Velocity.

the first Sort was made by a pendulum made after the manner of a fly counter poysed: which was seuerall times repeated with the Successe expected, there being made 12 vibrations with the weight of two ounces, and twenty four vibrations with the weight of 8 ounces and 48 vibrations with two pounds weight all in the Same time.

The other Sort was with running water whereby it appeard that the falling water was to be raised 4 times the height to run out wth Double the celerity. this Later was orderd to be repeated the next Day, because the vessell Leaking hindred somewt the exactness of the experiment. The Curator produced an instrument with a wheel to perform the same thing in a horizontal postureition [sic]. this way was orderd to be tryed the next meeting. --

mr Oldenb: read Letters. 1. from Heuelius - dated dec: 11. 1668 SV wherein the author - - - answers 7 querys proposed to him in a Letter by the Secretary from Mr Hooke concerning his Cometicall obseruations. 2ly &c -…

Terry Foreman  •  Link

One could say Mr Goodgroome came to sing for his supper, but he was there at dinner.

Franz Josef Elmer  •  Link

Royal Society: Is this the first experimental evidence that the kinetic energy is proportional to the square of the velocity?

Terry Foreman  •  Link

"Is this the first experimental evidence that the kinetic energy is proportional to the square of the velocity?"

It isn't recognised that way: The principle in classical mechanics that E ∝ mv2 was first developed by Gottfried Leibniz and Johann Bernoulli, who described kinetic energy as the living force, vis viva. Willem 's Gravesande of the Netherlands provided experimental evidence of this relationship.…

[I]n 1722 ['s Gravesande] published the results of a series of experiments in which brass balls were dropped from varying heights onto a soft clay surface. He found that a ball with twice the speed of another would leave an indentation four times as deep, from which he concluded that the correct expression for the "live force" of a body in motion (what is modernly called its "kinetic energy") is proportional to mv2.[5]…

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