https://physlab-wiki.com/ 2026-04-21T18:01:52+00:00 https://physlab-wiki.com/ https://physlab-wiki.com/lib/tpl/UChicago/images/favicon.ico text/html 2023-09-11T15:20:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/atwoods_machine?rev=1694460059&do=diff Atwood's Machine ---------- Two large masses joined by a string are suspended over a light, low-friction pulley. When an additional small amount of mass is added to one side the system clearly exhibits uniformly accelerated motion. Prepared demos text/html 2026-01-06T10:20:27+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/cavendish_balance?rev=1767712827&do=diff The gravitational attraction between two masses can be observed using a torsion balance, allowing the determination of the gravitational constant, G. For a detailed description of the apparatus, how to calibrate it, and how to perform measurements, see the attached document. text/html 2023-09-11T15:22:14+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/central-potential?rev=1694460134&do=diff Central Potential Not limited to Newton's laws, but it applies to the classical gravitational potential. This consists of a plastic rendition of the 1/r gravitational potential. Balls can be given some tangential velocity around the well and orbital motion can be observed; this serves to demonstrate the gravitational potential acting on planets in a solar system. text/html 2023-09-11T15:23:22+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/fan_cart?rev=1694460202&do=diff Fan Cart A small cart is driven by a battery-powered fan. When a magnetically-attached sail is installed in the path of the propelled air the cart ceases to move. Setup Make sure batteries have charge and that you position the sail is in the path of the air (not the side where it sucks air). text/html 2023-09-11T15:24:18+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/free-fall?rev=1694460258&do=diff Free Fall of feather and penny A feather and a penny are inside a tube that can be evacuated. When there's air inside the tube, one can see that the penny falls faster than the feather due to air resistance. When the tube is evacuated, both fall at the same rate. text/html 2022-07-29T15:48:34+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/hand_smash?rev=1659124114&do=diff Hand Smash ---------- A lead brick is placed on top of one's hand and then hit with a hammer used to demonstrate Newton's third law. Since the brick is much more massive than the hammer head, its resulting acceleration, and therefore the force that the hand feels due to the hammer's impact, are small. text/html 2021-09-15T11:25:52+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/inertia_ball_breaks_string?rev=1631719552&do=diff Inertia Ball Breaks String A heavy ball hangs from a string and two additional strings hang from the bottom of the ball. When one of the bottom strings is yanked very quickly it breaks due to the inertia of the ball. When the remaining bottom string is pulled very slowly the top string breaks since, in this case, the tension there is greater than that of the bottom string. text/html 2023-09-11T15:25:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://physlab-wiki.com/physicsdemos/mechanics/newtons_laws/tablecloth_trick?rev=1694460359&do=diff Tablecloth Trick A place setting is hardly disturbed when the tablecloth beneath it is yanked away. Setup Remember to pull perfectly parallel to the table!!! The heavier the bottoms of the plates and glasses, the easier it is to do the demo without breaking stuff. Good luck trying this with a full wine glass ;)