**Shift-II**

**Date of submission: 2 Jan., 2015**

1. How does the Young’s modulus change with rise in temperature?

2. A rain drop of radius r falls in air with a terminal velocity v. what is the terminal velocity of a rain drop of radius 3r?

3. Why does air bubble in water goes up?

4. A wire is stretches by a certain amount under a load. If the load and radius are both increased to four times, find the stretch caused in the wire?

5. Calculate the percentage increase in the length of a wire of diameter 2 mm stretched by a force of 1 kg F. Young’s modulus of the material of wire is 15×10^{10} N m^{-2}.

6. 27 identical drops of water are falling down vertically in air each with a terminal velocity of 0.15 m/s. If they combine to form a single bigger drop, what will be its terminal velocity?

7. Water at a pressure of 4×10^{10} N/m^{2} flows at 2 m/s through a pipe of 0.02 m^{2} cross sectional area which reduces to 0.01 m^{2}. What is the pressure in the smaller cross section of the pipe?

8. A liquid takes 10 minute to cool from 70^{0}C to 50^{0}C. How much time will it take to cool from 60^{0}C to 40^{0}C? The temperature of the surrounding is 20^{0}C.

9. Calculate the total pressure inside a spherical air bubble of radius 0.2 mm at a depth of 2 m below the surface of a liquid of density 1.1 g/cc and surface tension 50 dyne/cm. Atmospheric pressure is 1.1×10^{5} N/m^{2}.

10. Show that there is always excess of pressure on the concave side of the meniscus of a liquid. Obtain the expression for the excess of pressure inside (i) a liquid drop (ii) a liquid bubble.