Pokhara University
Level: Bachelor | Semester: Fall | Year: 2015
Programme: B.Sc. Environmental Management
Course: Introductory Physics

Full Marks: 100 | Pass Marks: 45 | Time: 3 Hrs
Candidates are required to give their answer own words as far as practicable. The figures in the margin indicates full marks.

Attempt all the questions:

1. (a) Define the terms electric current and current density. Derive an 9 expression of drift velocity in terms of current density. [9]
   (b) A ball is dropped from a height of 20m and rebounds with a velocity which is ¾ of the velocity with which it hits the ground. What is the time interval between the first and second bounces? [6]
2. (a) Define the laws of radioactive disintegration. Also derive the decay equation . [9]
   (b) Describe about the comparative study between α particles, β particles and γ rays. [6]
3. (a) What is Doppler’s effect? Derive an expression for the apparent frequency received by a stationary listener in still medium, when the sources is moving from the listener. [9]
   (b) A current of 1.5 A is passed through a wire of length 1m and diameter of 2mm. If the specific resistance is 2.42X10^-8Ωm, find the potential defference across the ends of the wire. [6]
4. (a) State and prove principle of conservation of energy. [9]
   (b) Calculate the energy in electron volt un a quantum of X-radiation of wavelength 0.15nm. (Given: h=6.62X10^-34Js, c=3X10^8m/c and e=1.6X10^-19C) [6]
5. a) Define linear, superficial and cubical expansivity. Establish relations between them. [9]
   (b) What amount of heat energy is required to convert 20gm of ice at -10°C into steam at 100°C ? (Given: Specific heat capacity of ice=0.5cal/gm°C, specific heat capacity of water=1cal/gm°C, latent heat of ice=80cal/gm, latent heat of vaporization = 540cal/gm) [6]
6. a) State and prove Bernoulli’s principle. [9]
   b) A body travels two equal distances with velocity 20m/s and 30m/s respectively. What will be its average velocity? [6]
7. Write short notes on any two: [5X 2]
   a) Radiation Hazards and safety precautions
   b) Global warming and green house effect
   c) Noise pollution, consequences and its controlling measures