Why are satellites placed into orbit at least 150 km above Earth's surface?

The particles that are found in the nucleus of an atom are

When using the scientist method, which step comes last?

Abus travels 280km south along a straight path with an average velocity of 88km/h to the south. the bus stops for 24 min, then it travels 210 km south with an average velocity of 75 km/h to the south. how long does the total trip last?