Please I need answers, will give the brainliest to the one who answers first! 1. Explain briefly how the micrometer screw gauge is used to measure small distances accurately

With i really need the correct answer!

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.

What does the law of conservation of mass state?