I give brainliest for the perfect awnser

6) H = m + mcT

m is 20

Hf is 336

c is 4.2

T is 25

so

    H = 20x336 + 20x4.2x25

 ANSWER IS,

                      H = 8820 J

5) m=5kg=5000gm

   ddifference in temp = 25 C

   Energy or Q = 7000J

To find heat capacity of the piece of metal,

                         heat capacity = 280 J

   To find specific heat capacity,

                          Q = mcT

          so,

0.11 m/s and 0.28 m/s should be correct

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.