SCHOOL OF INDIANA
HOME OF VISIONARIES
2014E.C 3rd QUARTER FINAL EXAM
SUBJECT PHYSICS
GRADE 11
Name ______________________Section ____ Date _______
Time allowed: - 2hr.
I. Write “True” if the statement is correct and “False” if it is incorrect.
1. The moment of inertia of an object about an axis that doesn’t pass through its centre of mass is
always greater than the moment of inertia about a parallel axis through its centre of mass.
2. When a mass is rotating in a plane about a fixed point, its angular momentum is directed along a line
tangential to the plane of rotation.
3. If the body is in rotational motion, then it is necessary that a torque be acting on it.
4. If the moment of inertia of a rotating object decreases its angular velocity also decreases assuming no
external torque is applied.
5. The position of centre of mass does not depend upon the shape, size, and distribution of the mass of
the body.
6. Work is done by a force in the direction perpendicular to the motion.
7. Without friction or work by an external force, the sum of the potential and kinetic energies of a body
is constant.
8. Less power is required while slowly lifting a box than while lifting it up quickly.
II. Choose the best answer from the given options.
9. A horizontal force of 10N, making an angle θ with the horizontal, and acting on an object displaces it
by 0.3m along the horizontal direction. If the object gains K.E. of 1.5J, what is the horizontal
component of the force?
A. 3N
B. 5N
C. 4N
D.3N
10. A particle moves from a point (-2i +5j) to (4j +3k) when a force of 4i+3j N is applied. How much
work has been done by the force?
A. 8J
B. 11J
C. 5J
D. 2J
11. 300 J of work is done in sliding a 2 Kg block up an inclined plane of height 10m. Work done against
friction is (Take g= 10m/s2)
A. 1000J
B. 200J
C. 100J
D. Zero
12. A force of (2i + 3j - k) N acts on a body for 5 second, produces a displacement of (3i+5j +k)m. What
was the power used?
A. 20 W
B. 4 W
C. 6 W
D. 4.2 W
13. From an automatic gun a man fires 360 bullets per minute with a speed of 100m/s. If each weighs
10g, the power of the gun is:
A. 400 W
B. 300 W
C. 100J
D. 2J
14. During a certain period of time, the angular position of a swinging door is described by Φ = 1 - 5t 3t2, where Φ is in radians and t is in seconds. Determine the angular acceleration of at t = 2 s in
rad/s2.
A. 0
B. -4
C. -6
D. -22
15. A 2g block attached to an ideal spring with a spring constant of 80 N/m oscillates on a horizontal
frictionless surface. When the spring is 4 cm shorter than its equilibrium length, the speed of the
block is 17m/s. The greatest speed of the block is:
A. 4m/s
B. 6m/s
C. 5m/s
D. 9m/s
16. Given below is a graph between a variable force (F) (along y-axis) and the displacement (X) (along
x-axis) of a particle in one dimension. The work done by the force in the displacement interval
between 0m and 30m is :
A. 275J
B. 400 J
C. 325 J
D. 300 J
17. Distinguish between conservative and non- conservative forces.
A. Work done by a conservative force is path dependent, whereas work done by nonconservative force does not depend on the path followed.
B. Work done by a conservative force along any closed path is zero, whereas the work done by
non-conservative force along a closed path is not zero.
C. Friction force is an example of conservative force, whereas spring force and gravitational
force are typical examples of non-conservative force.
D. A conservative force dissipates energy, whereas a non-conservative force does not.
18. During inelastic collision between two bodies, which of the following quantities always remain
conserved?
A. Total kinetic energy
C. Total mechanical energy
B. Total linear momentum
D. Speed of each body
19. A series of wrenches of different lengths is used on a hexagonal bolt, as shown below. Which
combination of wrench length and Force applies the greatest torque to the bolt?
A.
C.
B.
D.
20. A solid sphere of mass m is fastened to another sphere of mass 2m by a thin rod with a length of 3x.
The spheres have negligible size, and the rod has negligible mass. What is the moment of inertia of
the system of spheres as the rod is rotated about the point located at position x, as shown?
A. 3 mx2
B. 4 mx2
C. 5 mx2
D. 9 mx2
21. By what factor does the rotational K.E. of a uniformly rotating solid sphere be changed only because
of change in its axis of rotation from the centre to the edge of the sphere?
A. 3.5
B. 2.5
C. 2.0
D. Not changed
22. A 4kg uniform disk has a radius of 10cm starting from rest, it rotates about an axis under the action
of a constant torque of 0.4Nm. How long does the disk take to reach an angular speed of 120rad/s?
A. 1s
B. 2s
C. 4s
D. 6s
23. A ring, a coin and a solid sphere all have the same radius start from rest and roll down without
slipping from the top of an inclined plane at the same time. What is the order in which they reach the
bottom?
A. Ring, coin, and then sphere.
C. Sphere, ring, and then coin.
B. Coin, sphere, and then ring.
D. Sphere, coin, and then ring.
24. Identify the correct statement about torque and angular acceleration.
A. For the same time interval, a small torque and large torque change angular momentum by the
same amount.
B. A small torque applied for a longer time and a large torque exerted for a shorter time have the
same effect on the change of angular momentum.
C. No torque acts on an object when its angular momentum increases.
D. The change in angular momentum is inversely proportional to the torque exerted for a given
time interval.
25. A solid cylinder of radius 0.2 m and mass 2kg is at rest at a height 1.2 m at the top of an inclined
plane making an angle 60° with the horizontal. Assuming no slipping, what is the speed of the
cylinder at the bottom of the incline?
A. Zero
B. 6 m/s
C. 2 m/s
D. 4 m/s
26. A wheel starts from rest and rotates with constant angular acceleration to reach an angular speed of
12 rad/s in 3 s. What is the magnitude of the angular acceleration of the wheel in rad/s2 and the angle
in radians through which it rotates in this time interval respectively?
A. 4, 18
B. 3, 18
C. 18, 5
D. 18, 4
27. A solid sphere of mass m and radius R is rotating about its diameter. A solid cylinder of the same
mass and same radius is also rotating about its geometrical axis with an angular speed twice that of
the sphere. The ratio of their kinetic energies of rotation (𝐸𝑠𝑝ℎ𝑒𝑟𝑒/𝐸𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟) will be
A. 2 : 3
B.1 : 5
C.1 : 4
D. 3 : 1
28. The x and y coordinates of the centre of mass the three-particle system shown below are:
A. 1.3m, 1.7m
B. 1.4m, 1.9m
C. 1.9m, 2.5m
D. 1.4m, 2.5m
29. A 4kg block starts from rest on the positive x axis 3 m from the origin and thereafter has an
acceleration given by a = (2 î -ĵ)m/s2. At the end of 2 s its angular momentum about the origin is:
A. 0
B. (−24 kg m2 /s)k
C. (+48 kg m2 /s) k D. (−36 kg m2 /s) k
30. Rigid rods of negligible mass lying along the y axis connected three particles as shown in figure. The
system rotates about the x axis with an angular speed of 2.00 rad/s. What is the rotational kinetic
energy of the system?
A. 124J
B. 148 J
C. 184 J
D. 240 J
31. Possible unit of angular momentum is:
A. kg · m/s
C. Kg.m/s2
B. kg·m2/s2
D. kg·m2 /s
32. An impulsive torque of 20Nm acts for a short time, 0.01sec, on a rotating disk. What is the angular
impulse imparted on the disk?
A) 1kgm2/s
B) 0.2kgm2/s
C) 10kgm2/s
D) 1000kgm2/s
III. Write the most simplified answer for the following questions in the space provided.
33. Two bodies, A and B, have equal kinetic energies. The mass of A is four times that of B. The ratio of the
momentum of A to that of B is:__________
34. The moment of inertia of uniform rigid rod of mass M and length L about an axis perpendicular to the rod
1
through one end is___________ (I centre = 12ML2).
35. A spring with spring constant K when stretched through distance 2 cm the potential energy is U. If it is
stretched by 6cm. The potential energy will be________
36. A 200N force is applied at the end of a 50cm long spanner to tighten a bolt. If the bolt turns through half a
turn, how much work is done? __________
37.A thin circular ring of mass M and radius r and moment of inertia Mr2is rotating about its axis with a constant
angular velocity ω. Two objects each of mass m, are attached gently to the opposite ends of a diameter of the
ring. The ring rotates with angular velocity given by_____________
IV.
Solve the following problems showing all the necessary steps clearly.
38. A 1.0kg block collides with a horizontal weightless spring of force constant 2.75N/m as shown in figure. The
block compresses the spring 4.0m from the rest position. If the coefficient of kinetic friction between the
block and horizontal surface is 0.25, then find the speed of the block at the instant of collision. (use g=10m/s2)
39. A child stands at the centre of a turntable with his arms outstretched. The turntable is set rotating with an
angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and
thereby reduces his moment of inertia to 2/5 times the initial value? Assume that the turntable rotates without
friction.
40. The position vector of a particle of mass 2 kg is given as function r=30ti + (40t−5t2)j. Find the angular
momentum of the particle about the origin at t = 4 .
ANSWER SHEET
Subject: PHYSICS
GRADE 11
Name ______________________Section ____ Date _______
Part I
True or False
1. ___________
Part II
Choose
Part III
Blank space
2. ___________
9. ______
10. ______
17. ______ 25. ______
18. ______ 26. ______
33. _______________
34. _______________
3. ___________
11. ______
19. ______ 27. ______
35. _______________
4. ___________
12. ______
20. ______ 28. ______
36. _______________
5. ___________
13. ______
21. ______ 29. ______
37._______________
6. ___________
14. ______
22. ______ 30. ______
7. ___________
15. ______
23. ______ 31. ______
8. ___________
16. ______
24. ______ 32. ______
Part IV
Work out
38.
39.
40.