You are in charge of evaluating the safety (hazard) of a low water crossing. Traffic surveys show that the "Aaverage"vehicle using the crossing is semi-rectangular in shape (10 ft long, 5 ft wide, and 4.0 ft high - not including the distance from the roadway to the floor of the vehicle, 1.5 ft), and weighs approximately 3,000 lbs. Assume the vehicle, including the engine compartment is completely sealed. Each tire has about 1 ft by 0.67 ft of tire tread in contact with the road surface. Assume that the specific weight of the water flowing is 62.4 lb/ft3 (likely a low estimate since the water is carrying sediment). Given this information,
A. At what depth of flow will the vehicle just begin to float?
B. If the coefficient of static friction (cs) is 0.35; the coefficient of drag is 2.1 (length of vehicle is perpendicular to flow); the velocity of flow, regardless of depth, is 5 ft/s; and the total vehicle weight is equally distributed to all tires. Given this,
a. At what depth of flow does the vehicle begin to move?
b. Once the car begins to move, the coefficient of friction appropriate is the kinetic coefficient, do we care?
c. A tree moving with the flow now hits the vehicle. What force does this add to the situation?