Tudy the images about geologic time.

what is a noticeable difference between both eras?

the paleozoic era, not the mesozoic era, had the first dinosaurs.
the first mammals emerged in the paleozoic era, not the mesozoic era.
the mesozoic era, not the paleozoic era, had the first animals with shells.
the first flowering plants appeared in the mesozoic era, not the paleozoic era.

The first flowering plants appeared in the Mesozoic era, not the Paleozoic era.

Explanation:

The Mesozoic era was an era where numerous organisms started to develop in very unique and more advanced ways, both the animals and the plants. In the last period of the Mesozoic, the Cretaceous, the first flowering plants started to appear on the scene. This was revolutionary trait of the plants, and soon these plants started to occupy more and more space and became one of the dominant organisms on the planet. Other important evolution that took place in this period are the appearance of the dinosaurs and the mammals, both becoming the dominant animals on the planet, first the dinosaurs, after that the mammals.

wavelength variability is the right one

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.