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First Year/ First Semester
Subject:
Physics I
FM: 60
Time: 3 hours PM: 24
Candidates are required to give their answers in their own words
as far as practicable. The figures in the margin indicate full marks.
Year: 2066
1. Write the law of conservation
of momentum and the law of conservation of energy. Write Galilean transformation. Show that the laws of conservation of momentum and of conservation
of energy are invariant under
Galilean transformation. (2+1+4)
2. Write and explain Bernoulli’s theorem giving two practical examples.
Deduce Bernoulli’s equation. (1+2±2+2)
3. (a) Given the
sum of external forces acting upon a system of particles equals zero, show that the
total angular momentum remains constant. (4)
(b)
Write Gauss’s law for a system of charges in vacuum. Modify this law for the case when the some charges are in
medium of dielectric constant K. (1.5+2)
4. Derive the expression for energy
density in electric field. (7)
Derive Ñx E = - 
which constitutes one of the Maxwell’s equation. (7)
which constitutes one of the Maxwell’s equation. (7)Section B
Short Answer Questions:
Answer any eight:
5. Calculate the magnitude of centripetal
force acting on a mass 100g placed at a
distance 0.2m from the center of a
rotating disk with 200 rpm. (4)
6. Given g = 9.81 ms2, radius of earth = 6.38 x 106m and gravitational constant (G=6.6 x l0-11 m3 Kg s-2. Calculate the mass of the earth and time of revolution of a satellite in a circular orbit near the earth surface. (2+2)
7. A charged particle moving along x — axis enters a region in which a constant electric field is along y — axis
and a constant magnetic field is along z
— axis. What is the condition that the net force acting on the
charge is zero? (4)
8. A particle in Simple Harmonic Motion. Show
that the total energy of the
particle is constant. (4)
9. In an experiment with Poiseuille’s apparatus the volume
of water coming out per second is 8
cm3through a tube of
length 0.62 m and of uniform
radius 0.5 mm. The pressure
difference between the two ends of the
tube is equal to 3.1 cm
of Hg. You
can use the Poiseuille’s formula to calculate the
coefficient of viscosity
πr4P
(4)
Q= 8hl
10. Two point charges have charge q1= 2.0 x 10-8 C and q2=-0.7 x 10-8 C respectively.
The charges
are placed 2 cm apart. Find force between the charges. (4)
11. An electron having kinetic
energy 3.0 x 10-17 J enters a region
of space containing a uniform electric field E = 800 vm-1. The field
is parallel to the electron’s velocity and decelerates it. How far does the electron travel before it
comes to rest? (4)
12. A straight metal wire of length
1 is moved in a magnetic field
with velocity .
Consider the Lorentz force
acting electrons in the wire and show that the potential difference
across the wire is . x (4)
13. A capacitor C, a resistor R
and a battery arc connected in series with a switch.
The switch is closed at time
t = 0. Set up the differential equation governing charge on the capacitor and find the charge as a function of time. (4)
14.
Calculate the energy density of uniform magnetic field of
strength 1 Tesla in vacuum- [µ0=4πx10-7 ] (4)
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