Achild jumps on a trampoline. what causes the child to rise in the air

One object has a mass of 1 kg and another object has a mass of 3 kg. if the speeds are the same, which of the following is true about their kinetic energy?

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.

Mackinzie walks 4 blocks west, then 2 blocks south, then 4 blocks east, and,finally, 1 block south. what is the magnitude of her total displacement duringthis walk (in blocks)?