A50.0-kg box rests on a horizontal surface. the coefficient of static friction between the box and the surface is 0.300 and the coefficient of kinetic friction is 0.200. what is the friction force on the box if (a) a horizontal 140-n push is applied to it?

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.