The velocity ratio of a differential wheel and axle with D as the diameter of effort wheel and d_{1},and d_{2} as the diameters of larger and smaller axles respectively, is
When a body of mass moment of inertia I (about a given axis) is rotated about that axis with an angular velocity to, then the kinetic energy of rotation is
If a number of forces are acting at a point, their resultant is given by
The cartesian equation of trajectory is(where u = Velocity of projection, `alpha` = Angle of projection, and x, y = Co-ordinates of any point on the trajectory after t seconds.)
A number of forces acting at a point will be in equilibrium, if