You have two small sculptures made of copper and gold. The first sculpture has 5% gold while the second one has 10% gold. The first sculpture has twice the mass of the second one. You melt both, extract the gold and you make a ring of pure gold that is 10 g. What is the mass of the lighter sculpture?
a. 40g
b. 50g
c. 80g
d. 100g
e. 150g

7.45 a student is interested in the aerodynamic drag on spheres. she conducts a series of wind tunnel tests on a 10-cm-diameter sphere. the air in the wind tunnel is at 50 â°c and 101.3 kpa. she presents the results of her tests in the form of a correlation, đť’ź = 0.0015v1.92, where đť’ź is the drag force in newtons and v is the velocity in m/s. another student realizes that the results would have been more effectively presented in terms of dimensionless parameters, say, î  1 = f (î  2) = c î  a2 , where î  1 and î  2 are dimensionless parameters and c and a are constants. what are the most appropriate dimensionless parameters (î  1 and î  2) and the corresponding values of c and a? what would be the drag on a 2-cm-diameter sphere placed in a 1-m/s, 20 â°c water stream?