A wind tunnel is to be used with a 20 cm high model car to approximately reproduce the situation in which a 550 cm high car is moving at 15 mi *. What should be the wind speed in the tunnel?
(a) 2.41 km/*
(b) 3.41 km/*
(c) 0.41 km/*
(d) 5.41 km/*
Correct Option (c) 0.41 km/s
Explanation:
We want the Reynolds number NR to be the same in both cases, so that the situation is similar in both the cases, That is, we want
Both ρ and η are the same in the two cases, so we have
