Lars is jogging besides the railroad tracks at a speed of 2.00m/s when he hears a train whistles behind him at a frequency of 2115hz. if the actual frequency of the train whistle is 2000 hz, how fast is the train moving

Aplayground merry-go-round has a radius of 4.6 m and a moment of inertia of 200 kg-m2 and turns with negligible friction about a vertical axle through its center. a child applies a 26.0 n force tangentially to the edge of the merry-go-round for 15.0 seconds. if the merry-go-round is initially at rest, how much work did the child do on the merry-go-round?