Determine the pressure difference in tube of non-uniform cross sectional area as shown in figure.

$$\Delta P=?, d_1=5 \mathrm{~cm}, v_1=4 \mathrm{~m} / \mathrm{s}, d_2=2 \mathrm{~cm}, v_2=?$$

In an isothermal process 2 water drops of radius $$1 \mathrm{~mm}$$ are combined to form a bigger drop. Find the energy change in this process if $$T=0.1 \mathrm{~N} / \mathrm{m}$$.

Assertion : Water drops take spherical shape when falling freely.

Reason : Water has minimum surface tension among all liquids.

Assertion : Sometimes insects can walk on water.

Reason : The gravitational force on insect is balanced by force due surface tension.