Over due by alot please help

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Curious carl calculated the density of a cube to be 4.50 g/cm3. what is the density of the cube in g/l?

*drag each tile to the correct location in the sequence* the table shows chronological events in the life of our sun, a medium-sized star. place the missing events into the correct rows of the table.