Where does the word 'robot' come from?

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

Two students, each riding bicycles, start from the same apartment building and ride to the same building on campus, but each takes a different route. the first student rides 1100 m due east and then turns due north and travels another 1430 m before arriving at the destination. the second student heads due north for 1930 m and then turns and heads directly toward the destination. at the turning point, how far is the second student from the destination?

Which composition of water moves to begin a deepwater current?