A custodian pushes a 138 kg box across a level floor. The box moves at a constant velocity. The custodian pushes horizontally on the box with a force of 853 Newtons, what must be the friction force experienced by the box in Newtons?

Fossils: preserved remains of a living thing (mostly found in sedimentary rocks)
Crystals: a piece of a solid substance having a natural geometrical form ( found in igneous rocks and sedimentary (mostly igneous))
Gas bubbles: (igneous) made in a rock by eruptions or volcanoes
Glassy surface: of a rock looks like a block of glass (colored) also sometimes occurs because of volcanoes (igneous)
Foliation: (metamorphic rocks) layering in rocks; can be thin layering or thick
Sand or pebbles: (sedimentary) Sand: mineral particles of a rock Pebbles: a coast of a rock usually smooth