What do counties get their power from

Trumpeter a holds a b-flat note on the trumpet for a long time. person c is running towards the trumpeter at a constant velocity. person b is running away from the trumpeter at the same rate. person d is standing still the whole time. which person hears a frequency that is lower than the b-flat?

Aball has an initial velocity of 3 m/s. if there is no friction, what is the highest it could roll?

How do we measure or think of speed in the united states?