The analysis of spatial and temporal distribution patterns of the Permian Cathaysian flora has evidenced that the application of the equilibrium theory of island biogeography (ETIB) can be extended to palaeobiogeography (Wang et al .

This article mainly compared jouly steelyard and physical balance are applied in measuring the density of the method of hydrostatics,the results show that jouly steelyard have more advantage and innovation.

Based on the experimental teaching of using three-wire pendulum to measure the moment of inertia of objects for many times,this paper summarizes some pitfalls and solutions of secondary school students in three-wire pendulum experiment and points out that these problems can be solved from three aspects:rotation,physical balance and data processing forms.