Escapement may avoid the need for lubrication in the escapement (though it does not obviate the requirement for lubrication of other parts of the gear train). The accuracy of a mechanical clock is dependent on the accuracy of the timing device. If this is a pendulum, then the period of swing of the pendulum determines the accuracy. If the pendulum rod is made of metal it will expand and contract with heat, shortening or lengthening the pendulum; this changes the time taken for a swing. Special alloys are used in expensive pendulum-based clocks to minimize this distortion. The degrees of arc
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