A box of mass 3.06 kg slides down a rough vertical wall. The gravitational force on the box is 30 N . When the box reaches a speed of 2.5 m/s , you start pushing on one edge of the box at a 45? angle (use degrees in your calculations throughout this problem) with a constant force of magnitude Fp = 23 N , as shown in (Figure 1) . There is now a frictional force between the box and the wall of magnitude 13 N . How fast is the box sliding 2.8 s after you started pushing on it?

A/ Find the box's speed vf at 2.8 s after you first started pushing on it.

45