Kendriya Vidyalaya SECL Chirimiri

Half Yearly Examination, XI, Physics, 3 Hours, 70 marks (2023-24)

Section: A (1*16)
Q.1. For which of the following does the centre of mass lie outside the body ?
(a) A pencil (b) A shotput (c) A dice (d) A bangle
Q.2. When a disc rotates with uniform angular velocity, which of the following is not true?
(a) The sense of rotation remains same. (b) The orientation of the axis of rotation remains same.
(c) The speed of rotation is non-zero and remains same. (d) The angular acceleration is non-zero and remains same.
Q.3. A bicyclist comes to a skidding stop in 10m. During this process, the force on the bicycle due to the road is 200N and is
directly opposed to the motion. The work done by the cycle on the road is
(a) + 2000J (b) – 200J (c) zero (d) – 20,000J
Q.4. A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant
during the fall?
(a) Kinetic energy. (b) Potential energy. (c) Total mechanical energy. (d) Total linear momentum.
Q.5. During inelastic collision between two bodies, which of the following quantities always remain conserved?
(a) Total kinetic energy. (b) Total mechanical energy. (c) Total linear momentum. (d) Speed of each body.
Q.6. A ball is travelling with uniform translatory motion. This means that
(a) it is at rest. (b) the path can be a straight line or circular and the ball travels with uniform speed.
(c) all parts of the ball have the same velocity (magnitude and direction) and the velocity is constant.
(d) the centre of the ball moves with constant velocity and the ball spins about its centre uniformly.
Q.7. Conservation of momentum in a collision between particles can be understood from
(a) conservation of energy (b) Newton’s first law only (c) Newton’s second law only (d) both Newton’s second and third law
Q.8. The number of significant figures in 0.06900 is
(a) 5 (b) 4 (c) 2 (d) 3
Q.9. The sum of the numbers 436.32, 227.2 and 0.301 in appropriate significant figures is
(a) 663.821 (b) 664 (c) 663.8 (d) 663.82
Q.10. The numbers 2.745 and 2.735 on rounding off to 3 significant figures will give
(a) 2.75 and 2.74 (b) 2.74 and 2.73 (c) 2.75 and 2.73 (d) 2.74 and 2.74
Q.11. The mass and volume of a body are 4.237 g and 2.5 cm , respectively. The density of the material of the body in correct
3

significant figures is
(a) 1.6048 g cm–3 (b) 1.69 g cm–3 (c) 1.7 g cm–3 (d) 1.695 g cm–3
Q.12. A vehicle travels half the distance L with speed V1 and the other half with speed V2, then its average speed is
𝑉1 + 𝑉2 2𝑉1 + 𝑉2 2𝑉1𝑉2 𝐿(𝑉1 +𝑉2 )
(a) 2
(b) 𝑉 1 + 𝑉2
(c) 𝑉1 + 𝑉2
(d) 𝑉1 𝑉2
Directions: Each of these questions contain two statements, Assertion and Reason. Each of these questions also has four
alternative choices, only one of which is the correct answer. You have to select one of the codes (a), (b), (c) and (d) given below.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.
Q.13. Assertion: A spring has potential energy, both when it is compressed or stretched.
Reason: In compressing or stretching, work is done on the spring against the restoring force.
Q.14. Assertion: A force applied on the body always does work on the body.
Reason: If a force applied on a body displaces the body along the direction of force work done will be maximum.
Q.15. Assertion: When an algebraic equation has been derived, it is advisable to check it for dimensional consistency.
Reason: This guarantees that the equation is correct.
Q.16. Assertion: Two particles of different mass, projected with same velocity at same angles. The maximum height attained by
both the particle will be same.
Reason: The maximum height of projectile is independent of particle mass.
Section: B (2*5)
Q.17. Why is it easier to pull a lawn roller than to push it? Explain.
Q.18. A particle moves along the X-axis from x=0 to x=5 m under the influence of a force given by F = 7 − 2x + 3x2 . Find the
work done in the process.
Q.19. Write difference among elastic collision, inelastic collision and perfectly inelastic collision.
Q.20. Find the torque of a force 7𝑖 − 3𝑗 − 5𝑘 about the origin which acts on a particle whose position vector is 𝑖 + 𝑗 − 𝑘
Q.21. Calculate the moment of inertia of the earth about its diameter, taking it to be a sphere of 1025 kg and diameter 12800 km.
Section: C (3*7)
Q.22. Obtain an expression for the centripetal force F acting on a particle of mass m moving with velocity v in a circle of radius r.
Take dimensionless constant K=1.
Q.23. Two vectors 𝐴⃗ and 𝐵⃗ are inclined to each other at an angle θ. Using parallelogram law of vector addition, find the
magnitude and direction of their resultant.
Q.24. A projectile is fired with a velocity u making an angle θ with the horizontal. Show that its trajectory is a parabola.
Q.25. Three masses 3, 4 and 5 kg are located at the corners of an equilateral triangle of side 1m. Locate the centre of mass of
the system.
Q.26. Prove that the maximum horizontal range is four times the maximum height attained by the projectile, when fired at an
inclination so as to have maximum horizontal range.
Q.27. Derive an expression for acceleration due to gravity at depth d from earth surface.
Q.28. Derive an expression for the gravitational potential energy of a body of mass m located at distance r from the centre of
the earth.
Section: D (4*2)
Q.29. Case Study Based: Keplar’s Law
LAW OF ORBIT: The orbit of every planet is an ellipse around the sun with sun at one of the two foci of ellipse.
LAW OF AREAS: The line that joins a planet to the sun sweeps out equal areas in equal intervals of time. Area covered by the
planet while revolving around the sun will be equal in equal intervals of time. This means the rate of change of area with time is
constant.
LAW OF PERIOD: According to this law the square of time period of a planet is directly proportional to the cube of the semi-
major axis of its orbit. Suppose earth is revolving around the sun then the square of the time period (time taken to complete
one revolution around sun) is directly proportional to the cube of the semi major axis.It is known as Law of Periods as it is
dependent on the time period of planets. The force of attraction between any two unit masses separated by a unit distance is
called universal gravitational constant denoted by G measured in Nm2/kg2.
Answer the following:
1) Kepler’s second law is knows as -
a) Law of period b) Law of area c) Law of gravity d) None of these
2) Kepler’s third law is knows as -
a) Law of period b) Law of area c) Law of gravity d) None of these
3) The velocity of a planet is constant throughout its elliptical trajectory in an orbit -
a) True b) False c) None of these
4) Two objects of masses 5kg and 10 kg separated by distance 10 m. What is gravitational force between them?
Q.30. Case Study Based: Projectile Motion
Projectile motion is a form of motion in which an object or particle is thrown with some initial velocity near the earth’s surface and it moves
along a curved path under the action of gravity alone. The path followed by a projectile is called its trajectory, which is shown below. When a
projectile is projected obliquely, then its trajectory is as shown in the figure

below.
Here velocity u is resolved into two components, we get (a) u cos θ along OX and (b) u sin θ along OY .
(i) The example of such type of motion is
(a) motion of car on a banked road (b) motion of boat in sea
(c) a javelin thrown by an athlete (d) motion of ball thrown vertically upward
(ii) The acceleration of the object in horizontal direction is
(a) constant (b) decreasing (c) increasing (d) zero
(iii) The vertical component of velocity at point H is
(a) maximum (b) zero (c) double to that at O (d) equal to horizontal component
(iv) A cricket ball is thrown at a speed of 28 m/s in a direction 30° with the horizontal. The time taken by the ball to return to the
same level will be: (a) 2.0 s (b) 3.0 s (c) 4.0 s (d) 2.9 s
Section: E (5*3)
Q.31. Derive all three equations of motion for uniformly accelerated motion from velocity-time graph.
Q.32. What do you mean by banking of a curved road? Determine the maximum safe velocity with which a vehicle can negotiate
a circular road of radius r and banked at an angle θ. Frictional forces are also taken into account.
Q.33. Show that the total mechanical energy of a freely falling body remains constant throughout its fall. Also plot graph for
kinetic energy, potential energy and total mechanical energy during free fall of a body.