Escapement and watches. These are described individually below. Although the invention of the crystal oscillator and the quartz clock in the 1920s shifted technological research in timekeeping to electronic methods, major advances in the design of mechanical escapement are still happening. Coaxial escapement, invented by English watchmaker George Daniels around 1974 and patented in 1980 has rather dramatically increased the accuracy and durability of mechanical watches. Yoshikazu Akahane with teams of engineers at Seiko Epson developed the spring drive movement around 1977, and obtained not less than 230 patents between 1982 and the present. The reliability of an escapement depends on
Mechanical energy mechanical energy of the colliding objects has been converted into an equal amount of heat. Thus, the total energy of the system remains unchanged though the mechanical energy of the system has reduced. A satellite of mass formula_4 at a distance formula_5 from the centre of Earth possesses both kinetic energy, formula_6, (by virtue of its motion) and gravitational potential energy, formula_7, (by virtue of its position within the Earth’s gravitational field; Earth's mass is formula_8). Hence, mechanical energy formula_9 of a satellite is given by If the satellite is in circular orbit, the energy conservation equation can be further