Why newton’s first law is sometimes called the law of inertia?
a.)because inertia is the same thing as friction
b.)because inertia is the tendency of objects to resist changes in their motions
c.)because inertia describes the application of force to an object in motion
d.)because inertia describes the application of force to an object at rest

Consider a double atwood machine constructed as follows: a mass 4m is suspended from a string that passes over a massless pulley on frictionless bearings. the other end of this string supports a second similar pulley, over which passes a second string supporting a mass of 3m at one end and m at the other. using two suitable generalized coordinates, set up the lagrangian and use the lagrange equations to find the acceleration of the mass 4m when the system is released. explain why the top pulley rotates even though it carries equal weights on each side.