PHYSICS
(312)
TUTOR MARKED ASSIGNMENT

1- Answer any one out of the following questions in about 40-60 words.

a- A =3i 4j 

and B=i – j

, are two vectors in x – y plane. Find the magnitude of the sum of
these two vectors. (See Lesson- 1)

b- The position of a particle moving in a straight line is given by x = 3 + 4t + 3t2
, where x is in
metre and time is in second. Find the values of the following physical quantities for the particle
at t = 2s. (See Lesson- 2)
(i) Position
(ii) Displacement
(iii) Velocity
(iv) Acceleration

2- Answer any one of the following questions in about 40 -60 words.

a- Three particles each of mass 5 g are placed at the vertices of an equilateral triangle of side
60 cm. Find: (See Lesson- 7)
(i) Distance of its centre of mass from any of its vertex
(ii) Moment of inertia of the system of particles about an axis passing through the centre of
mass of the system and perpendicular to the plane containing them.

b- Explain the concept of modulation and its need in long distance communication.
(See Lesson- 30)

3- Answer any one of the following questions in about 40 -60 words

a- An astronomical object has its mass 4 times the mass of earth and radius half of the radius of
earth. If acceleration due to gravity at earth is g, find its value at the surface of the astronomical
object. (See Lesson- 5)

b- Find an expression for the energy density in terms of stress and strain. (See Lesson- 8)

4- Answer any one out of the following questions in about 100-150 words.

a- A person with external body temperature 35°C is present in a room at temperature 25°C.
Assuming the emissivity of the body of the person to be 0.5 and surface area of the body of the
person as 2.0 m2
, calculate the radiant power of the person. (See Lesson- 12)

b- An equiconvex lens (of refractive index 1.5) is placed in contact with plane mirror as shown in
the figure. A small needle with its tip on the principal axis is moved along the axis until its
inverted image is found at the position of the needle. The distance of the needle from the lens
is measured to be 30 cm. Now a few drops of a liquid are put in between the lens and the
plane mirror and the new position of the image is found to be located at 45 cm. Calculate the
refractive index of the liquid. (See Lesson- 20)

 5- Answer any one of the following questions in about 100–150 words. 4

a- A closed vessel having capacity 200 mL is filled with hydrogen gas at STP. Calculate
(See Lesson- 10)
(i) Number of moles of hydrogen gas filled in the vessel.
(ii) Pressure of hydrogen gas in the vessel at 273°C.
(iii) Root mean square velocity of hydrogen gas at STP.
(iv) The value of Cp and Cv for hydrogen gas

With the help of a neat labelled ray diagram, show the image formation by a compound microscope
when the final image is formed at the least distance of distinct vision. Write the expression for its
magnifying power in terms of parameters related to the microscope.
(See Lesson- 23)

6- Prepare any one project out of the given below.

a- Take a hollow plastic ball (dia 3 cm to 5 cm). Using a needle pass a thread of about 105 cm
along a diameter of the ball. Tie a knot at one end. Hang the ball from a rigid support so that the
ball is free to oscillate. Make a small hole (5 mm dia) in the ball near the top. Fill it with sand
and find its time period of oscillation. Empty the ball and fill it with steel balls/iron filings and
repeat the experiment. Similarly carry out the experiment with common salt. Compare the time
periods obtained in the above three cases. What do you find? Explain your finding.
(See Lesson- 13)

b- Directions: This project should be performed in an open ground.
Take a plastic pipe and fix a jet at one of its end. Connect the pipe to a water tap attached to
a large overhead tank. Fix a large protractor as shown in the figure so that you can hold the
pipe at different angles (say at 150
, 300
, 450
and 600
).
Hold the pipe in such a manner that jet of water comes out at an angle of 150
. Measure the
distance up to which water is reaching. This is the range of the projectile.
Now hold the pipe at an angle of 300
, 450
and 600
. Measure the range of the projectile in each
case. Keep the speed of water coming out of the jet same in each case.
What do you find? For a given speed, the range is maximum when the angle of projection is
450
.
Also, try to find out the effect of initial speed of water on the range of the projectile.
(See Lesson- 4)