5. the picture shows a crane holding a crate in the air. neither the crane in the air now the crate is moving. which set of arrows correctly illustrates the forces acting on the crane?

Can someone explain to me how to do this problem ?

Aball with a mass of 275 g is dropped from rest, hits the floor and rebounds upward. if the ball hits the floor with a speed of 2.40 m/s and rebounds with a speed of 1.70 m/s, determine the following. (a) magnitude of the change in the ball's momentum (let up be in the positive direction.)

When using the scientist method, which step comes last?