Launching a rock from a tower with height equal to Earth's radius. Air resistance is ignored, but variation of gravitation is not. First rock is just dropped. Then a rock is given some tangential speed. When the initial angular velocity is about five times the angular velocity of the Earth, a rock gets into orbit around the Earth. When this ratio is about six, the orbit becomes circular.
Continuing, the break-off angle of an accelerating sphere is smaller. Three values of acceleration are depicted, relative to g: 0.1, 0.5, and 2.0.
A wheel rolls on a horizontal surface without slipping. Also rolling is the acceleration vector (red). It has two components. Tangential acceleration (orange) changes the magnitude of the velocity vector of a point on the rim of the wheel. Normal acceleration (green) changes its direction.
Note: this is from Irodov, problem 1.52., where it says that acceleration is constant in magnitude and pointing permanently towards the center of the wheel. I humbly disagree. Please comment.
Triangle must be the top. (after szimmetria-airtemmizs)
A brick expands as it is repeatedly heated and cooled down. Horizontal ground sees the brick remaining still as the force of friction on the expanding right half of the brick balances the force of friction on the expanding left half of the brick. Forces are similarly balanced during the cooling. However, with the ground inclined the left and right directions along the slope are no longer considered equal as gravity breaks the symmetry, and the brick slowly moves down the slope. The animation wildly exaggerates the displacement. Using realistic data, my snail-brick travels about 0.2% of its length during a heating cycle.
