Assuming that the mass m of the largest stone that can be moved by a flowing river depends upon the velocity v of the water, its density \(\rho\). and the acceleration due to gravity g. Then m is directly proportional to :

v3 v4 v5 v6

v6

m \(\propto v^a \rho^p g^c\) [M] \(\propto\) [LT-1]a [ML-3]b [LT-2]c Comparing : a = 6; b = 1; c = -3 \(\Rightarrow\) m \(\propto\) v6