A psychologist is interested in exploring the effect tutorial support on students academic performance and assign students in to two groups. students in group one get the tutorial support and those in group two do not. In this example what is dependent variable, independent variable, control groupand experimental group​

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.