A construction worker places a compass at various positions on a wall until the compass needle deflects to one direction. What is the worker most likely using a compass to find? Changes in wall pressure The wood behind the wall Earth's magnetic field Sources of electrical current

The drag force, fd, imposed by the surrounding air on a vehicle moving with velocity v is given by fd = cdaρv 2/2 where cd is a constant called the drag coefficient, a is the projected frontal area of the vehicle, and ρ is the air density. an automobile is moving at v = 80 kilometers per hour with cd = 0.28, a = 2.3 m2, and ρ = 1.2 kg/m3.