A horizontal spring with spring constant 85 N/m N/m extends outward from a wall just above floor level. A 8.5 kg kg box sliding across a frictionless floor hits the end of the spring and compresses it 6.5 cm cm before the spring expands and shoots the box back out. How fast was the box going when it hit the spring?

Place me with this question is my last question

Una carga puntual de 3 x 10-6 c se coloca a 12 cm de una segunda carga puntual de - 1,5 x 10-6 c. calcular la magnitud fuerza eléctrica entre las cargas

Asolid cylinder and a cylindrical shell have the same mass, same radius, and turn on frictionless, horizontal axles. the cylindrical shell has light-weight spokes connecting the shell to the axle. a rope is wrapped around each cylinder and tied to blocks of equal masses that are held the same height above the ground. both blocks are released simultaneously. the ropes do not slip. which block hits the ground first? or is it a tie?