| Questions | 5 |
| Topics | Acceleration, Cell Division, Kuiper Belt, Mesosphere, Veins |
Acceleration is the rate of change of velocity per unit of time. In physics, the delta symbol (\(\Delta\)) represents change so the formula for acceleration becomes \(\vec{a} = { \Delta \vec{v} \over t }\)
Cell division is the process by which cells replicate genetic material in the nucleus. Cell division consists of several phases:
| Phase | Major Process |
|---|---|
| interphase | chromosomes replicate into chromatids and the cell grows |
| prophase | chromatids pair up |
| metaphase | paired chromatids move to opposite sides of the cell |
| anaphase | cell elongates and nucleus begins to separate |
| telophase | separation of nucleus is complete resulting in two new nuclei |
| cytokinesis | cytoplasm and cell membranes complete their separation resulting in two separate cells |
The Kuiper Belt is similar to the asteroid belt but much larger. Extending beyond the orbit of Neptune, it contains objects composed mostly of frozen methane, ammonia, and water. Most notably, the Kuiper Belt is home to Pluto, a dwarf planet that, until a 2006 reclassification, was considered the ninth planet of the solar system.
In the mesosphere, temperature again drops as altitude increases until the coldest point in the Earth's atmosphere, the mesopause, is reached where temperatures fall to −225 °F (−143 °C).
Veins carry blood back to the heart from the body. While arteries are thick-walled because they carry oxygenated blood at high pressure, veins are comparatively thin-walled as they carry low-pressure deoxygenated blood. Like the heart, veins contain valves to prevent blood backflow.