A road haulage truck has an approximate rectangular frontal area 2.5 m wide by 3.8 m high. To investigate the drag on the truck, a one – fifth scale model is to be tested in a wind tunnel. We can assume that the density and viscosity of the air are the same for the model as for the full size truck. If the truck travels at 120 km/h, what is the appropriate air speed for the model in the wind tunnel?

The lift on a spinning circular cylinder, in a freestream with a velocity of 10m/s, is measured as L, at standard sea level conditions and L, at an altitude of 10,000ft. (Assume that both cases generate the same circulation around the cylinder.) How do you compare L, and L2? Please choose one of the following alternatives: (1) L1 = L2 (ii) L1 > L2 (iii) L1 < L2 (iv) None of them O i O i O i O iv

F₂ Figure 1: Problem 6.

A block, as shown below, is sliding on a thin horizontal layer of water (u = 1.68 x 103 kg/m.s) between ice and the block with a speed of 13 m/s. The thickness of the water layer is 3.32 x 10-5 m. Given the following dimensions of the block, what is the force (F) required to maintain this movement? A = 9 cm B = 9 cm C= 8 cm B 2.96 N 5.33 N 4.14 N 4.74 N

When disturbed, a floating buoy will bob up and down atfrequency f . Assume that this frequency varies with buoymass m , waterline diameter d , and the specific weight γ ofthe liquid. ( a ) Express this as a dimensionless function. ( b )If d and γ are constant and the buoy mass is halved, howwill the frequency change?

The drag on a 2-m-diameter satellite dish due to an 69-km/hr wind is to be determined through a wind tunnel test using a geometrically similar 0.4-m-diameter model dish. Assume standard air for both model and prototype. (a) At what air speed should the model test be run? (b) With all similarity conditions satisfied, the measured drag on the model was determined to be 152 N. What is the predicted drag on the prototype dish? (a) Vm = (b) D = i i km/hr N