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$The wavelength \lambda of a wave depends on the speed v of the wave and its frequency f .Knowing that [\lambda]=[L][v]=\left[L T^{-1}\right] and [f]=\left[T^{-1}\right] Decide which of the following is correct f=v \lambda or f=v / \lambda$

$Name several repetitive phenomenon occurring in nature which could serve as reasonable time standard.$

$EXAMPLE 1.6Find the dimensions and hence the SI units of coefficient of viscosity \eta in the relation of Stokes law for the drag force F for a spherical object of radius r moving with velocity v given as F=6 \pi \eta rv.$

What are the dimensions and units of gravitational constant G in the formula?$F=G \frac{\mathbf{m}_{1} \mathbf{m}_{2}}{\mathbf{r}^{2}}$

$(b) How many nanoseconds in 1 year?$

$Does dimensional analysis give any information on constant of proportionality that may appear in an algebraic expression? Explain.$

$EXAMPLE 1.4Check the correctness of the relation v=\sqrt{\frac{F \times l}{m}} where V is the speed of transverse wave on a stretched string of tension \mathrm{F} length l and mass \mathrm{m} .$