A truck T has a weight of 8,000 lb and is traveling along a portion of a road

defined by the lemniscate r

2 = 0.2(106)

cos 2θ , where r is measured in feet

and θ is in radians. If the truck

maintains a constant speed of vr = 4 ft/s,

determine the magnitude of the

resultant frictional force which must be

exerted by all the wheels to maintain

the motion when = 0