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# Physics XI

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 15×1010 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 4×1010 N/m2 flows at 2 m/s through a pipe of 0.02 m2 cross sectional area which reduces to 0.01 m2. What is the pressure in the smaller cross section of the pipe?

8. A liquid takes 10 minute to cool from 700C to 500C. How much time will it take to cool from 600C to 400C? The temperature of the surrounding is 200C.

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 1.1×105 N/m2.

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.