Question

Kai was 200 meters north of the library when he remembered he had to return some books to the library. It took him 200 seconds to do the round trip.

Which best describes Kai’s roundtrip?

His speed was 1 m/s, and his velocity was 0.
His speed was 2 m/s, and his velocity was 0.
His speed was 1 m/s, and his velocity was 1 m/s north.
His speed was 2 m/s, and his velocity was 2 m/s south.

Answer 1

Total distance = 200 m to the library + 200 m back = 400 m.
Speed = distance / time = 400 m / 200 s = 2 m/s.
Displacement = 0 (he ended where he started), so velocity = 0 m/s.

Answer: His speed was 2 m/s, and his velocity was 0.