Category: Class 11 Physics Objective Questions

250+ TOP MCQs on Theorems of Perpendicular and Parallel Axes | Class 11 Physics

Physics Multiple Choice Questions on “Theorems of Perpendicular and Parallel Axes”.

1. A planar body is lying in the xz plane. What is the relation between its moment of inertia along the x, y & z axes?
a) Iz = Ix + Iy
b) Ix = Ix + Iz
c) Iy = Ix + Iz
d) Iz = Ix = Iy, because body is planar
Answer: c
Clarification: The body is lying in the xz plane. The perpendicular axis theorem states that the moment of inertia of a planar body about an axis perpendicular to its plane is equal to the sum of moment of inertia about two perpendicular axes in the plane of the body. Iy is perpendicular to plane of body, so Iy = Ix + Iz.

2. Perpendicular axis theorem can be applied for which of the following bodies?
a) Ring having radius R & negligible cross section
b) Disc of radius R and thickness t
c) Cylinder of radius R and height h
d) A cube of side ‘a’
Answer: a
Clarification: Perpendicular axis theorem can only be applied to planar bodies. From the given options only the ring is planar.

3. Consider two perpendicular axis in the plane of a planar body, such that I1 = 2 I2. The moment of inertia about an axis perpendicular to the plane and passing through intersection of I1 & I2 is 9kgm2. Find the value of I1& I2.
a) I1 = 9kg m2, I2 = 4.5kgm2
b) I1 = 3kg m2, I2 = 6kg m2
c) I1 = 6kg m2, I2 = 3kg m2
d) I1 = 18kg m2, I2 = 9kg m2
Answer: c
Clarification: By perpendicular axis theorem: 9 = I1 + I2 = 3 I2.
∴ I2 = 3kgm2 & I1 = 2*3 = 6kgm2.

4. The moment of inertia of a planar disc about a diameter is 8kgm2. What is the moment of inertia about an axis passing through its centre and perpendicular to the plane of disc?
a) 8kgm2
b) 16kgm2
c) 4kgm2
d) 2√2kgm2
Answer: b
Clarification: The moment of inertia about any diametrical axis will be the same. So, we can consider two perpendicular diameters and use the perpendicular axis theorem to get the moment of inertia about the axis which is perpendicular to the plane.
Thus, moment of inertia = 8+8
= 16kgm2.

5. Let I1 be the moment of inertia about the centre of mass of a thick asymmetrical body. Let I2 be the moment of inertia about an axis parallel to I1. The distance between the two axes is ‘a’ & the mass of the body is ‘m’. Find the relation between I1 & I2.
a) I2 = I1 – ma2
b) I1 = I2 – ma2
c) I2 = I1
d) Parallel axis theorem can’t be used for a thick asymmetrical body
Answer: b
Clarification: Parallel axis theorem can be used for any body. The parallel axis theorem states that moment of inertia about an axis perpendicular to an axis passing through centre of mass is given by:
I = ICOM + ma2, where m is mass of the body & ‘a’ is the distance between the axes. So, I2= I1 + ma2 OR I1 = I2 – ma2.

6. What is the moment of inertia of a rod, of mass 1kg & length 6m, about an axis perpendicular to rod’s length and at a distance of 1.5m from one end?
a) 0.75kgm2
b) 3kgm2
c) 5.25kgm2
d) 14.25kgm2
Answer: c
Clarification: Moment of inertia about an axis perpendicular to length and passing through COM is equal to MI2/12. To find I about given axis, we use parallel axis theorem,
I = ICOM + ma2, where a is the distance between the axis and m is mass of the body.
I = MI2/12 + Ma2
= 1*36/12 + 1*2.25
= 3 + 2.25 = 5.25kgm2.

7. The moment of inertia of a ring about a tangent is 4kgm2. What is the moment of inertia about an axis passing through the centre of the ring and perpendicular to its plane? Mass of the ring is 2kg & diameter is 2m.
a) 2kgm2
b) 4kgm2
c) 8kgm2
d) 1kgm2
Answer: b
Clarification: Using parallel axis theorem we can find I about centre of mass.
∴ I = 4 – 2*1 = 2kgm2.
Now using perpendicular axis theorem we get I1 about the desired axis.
∴ I1 = I + I = 4kgm2.

8. The moment of inertia of a planar square about a planar axis parallel to one side is 10kgm2. What is the moment of inertia about a diagonal?
a) 10kgm2
b) 5kgm2
c) 20kgm2
d) 1kgm2
Answer: a
Clarification: Using perpendicular axis theorem we can say that sum of moment of inertia about two perpendicular axes will be the same as sum of moment of inertia about other 2 perpendicular axes. Let I1 be the moment of inertia about a diagonal, we can say:
I1 + I1= 10 + 10 = 20kgm2
Or I1 =10kgm2.

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250+ TOP MCQs on Gravitation – Weightlessness | Class 11 Physics

Physics Quiz on “Gravitation – Weightlessness”.

1. For an object experiencing weightlessness _____
a) its weight force is non-zero
b) it has inertia
c) it experiences a value of acceleration greater than the acceleration due to gravity
d) it experiences a value of acceleration lesser than the acceleration due to gravity
Answer: b
Clarification: Since the object has mass, it always has inertia. However, weight force is zero and hence the experienced acceleration is zero because it is experiencing weightlessness.

2. Why do the astronauts in the international space station experience weightlessness?
a) The acceleration due to gravity at that height is zero
b) They are falling towards the earth
c) They have specially designed spacesuits for this purpose
d) The gravity of the moon and earth cancel out at that altitude
Answer: b
Clarification: The parabolic trajectory of the free fall of the international space station is at such high velocity that it essentially orbits the planet. The weightlessness experienced by the astronauts in the ISS is the consequence of this freefall.

3. An object is weightless inside a uniform spherical shell.
a) True
b) False
Answer: a
Clarification: The net acceleration due to gravity is zero at all points inside a uniform spherical shell because of which an object is weightless. This is because the sum of gravitational force vectors from all sides of the object is zero inside the shell.

4. A person sitting in a chair in a satellite feels weightless because _____
a) the earth does not attract the objects in a satellite
b) the normal force by the chair on the person balances the earth’s attraction
c) the normal force is zero
d) the person in the satellite is not accelerated
Answer: c
Clarification: Since the person sitting in the chair in the satellite is essentially in freefall along with the satellite, he does not experience any reaction force. The lack of reaction force (or) normal force makes a person feel weightless.

5. How do astronauts define “up” or “down” in space?
a) There is no “up” or “down” in space
b) The side facing the earth is “down” and the opposite side is ‘up”
c) “up’ or “down” is decided by the control centre on earth
d) The direction of the spacecraft’s power source is “up” and the opposite side is “down”
Answer: a
Clarification: There is no “up” or “down” in space due to the lack of normal reaction forces for their weights. Gravity defines the vertical direction. Thus for the astronauts, all directions are the same.

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250+ TOP MCQs on Thermal Properties of Matter – Specific Heat Capacity | Class 11 Physics

Physics Multiple Choice Questions on “Thermal Properties of Matter – Specific Heat Capacity”.

1. If we supply equal amounts of heat to equal masses of two different substances, the rise in temperature will be the same for both. True or False?
a) True
b) False
Answer: b
Clarification: Each body has a heat capacity which indicates the amount of heat it requires to raise its temperature by 1°C. Different substances require different amounts of heat for the same rise in temperature.

2. Why is water used in automobiles as a coolant?
a) It is not toxic for the environment
b) It has a high specific heat capacity
c) It has a high lubricating property which in turn keeps the engine cool by reducing friction
d) It is available in abundance
Answer: b
Clarification: Water has a high specific heat capacity because of which it can absorb large amounts of heat before increasing its temperature. Hence, it is used as a coolant.

3. Specific heat capacity depends on the mass of the substance. True or False?
a) True
b) False
Answer: b
Clarification: Specific heat capacity is defined as the heat capacity per unit mass for a substance. s = ΔQ/mΔT. So, no matter what mass of a substance we take ‘s’ will be equal to (ΔQ/ΔT) divided by that mass, which means ‘s’ doesn’t depend on the mass.

4. CP > CV always. True or False?
a) True
b) False
Answer: a
Clarification: When heat is added at constant pressure the heat is used to increase temperature and increase volume or we can say does work. But when heat is added at constant volume the heat only increases temperature and volume remains the same (work = 0). So For the same rise in temperature at constant pressure we have to provide more heat.

5. What is the relation between molar heat capacities of the two processes given in the diagram below? Assume process acb has a heat capacity of C1 and process adb has a heat capacity of C2.

a) C1 > C2
b) C2 > C1
c) C1 = C2
d) C1 = C1/ Area inside curve
Answer: b
Clarification: As the start and end points are the same for both processes, the temperature rise will be the same. The work done in process adb is more than that done in process acb. Therefore heat supplied will be less in process acb, so C2 > C1.

6. A closed container contains 0.6m3 of neon gas at 200K temperature and 1.3*105Pa. Find the rise in temperature when 8360 J of heat is supplied to it. The molar heat capacity of neon at constant volume is 3.2calK-1mol-1. Assume the container doesn’t expand on heating.
a) 13.3K
b) 15.8K
c) 13.9K
d) 15K
Answer: a
Clarification: no. of moles of neon gas = pV/RT
= (1.3*105*0.6) / (8.31*200)
= 46.9 moles ≅ 47 moles
ΔQ = nCVΔT ΔT = ΔQ/nCV
= (8360/4.18) / (47*3.2)
= 13.3K.

7. CV of a gas is 8 calK-1mol-1. Find CP/CV. Assume R = 2 calK-1mol-1.
a) 1.4
b) 1.33
c) 1.25
d) 1.8
Answer: c
Clarification: CP = CV + R = 8 + 2
= 10 calK-1mol-1.
CP/CV= 10 / 8 = 1.25.

250+ TOP MCQs on Kinetic Theory – Molecular Nature of Matter | Class 11 Physics

Physics Question Bank for Class 11 on “Kinetic Theory – Molecular Nature of Matter”.

1. What is meant by mean free path?
a) It is the average distance a molecule travels without colliding
b) Average distance between 2 molecules
c) Average distance travelled by a molecule before colliding with a wall of the container
d) Sum of distance travelled by all molecules
Answer: a
Clarification: Mean free path of a molecule is defined as the average distance travelled by molecules before colliding.

2. Which of the following states of matter has the maximum value of mean free path?
a) Gas
b) Solid
c) Liquid
d) Plasma
Answer: a
Clarification: The atoms of gas have the most interatomic space and can therefore travel freely. This is why they travel longer distances without colliding and are therefore said to have the maximum mean free path.

3. John Dalton said that atoms are the smallest constituents of elements. True or False?
a) True
b) False
Answer: a
Clarification: Dalton had proposed the atomic theory to explain the laws of definite and multiple proportions. He said that atoms are the smallest constituents of elements.

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250+ TOP MCQs on Principle of Superposition of Waves | Class 11 Physics

Physics Multiple Choice Questions on “Principle of Superposition of Waves”.

1. y1 = 2sin(3x – 2t) & y2 = 3sin(3x – 2t + π/4). Find the expression for resultant displacement caused by superposition of the two waves.
a) 3.6sin(2x-3t+3π/7)
b) 4.63sin(3x-2t+3π/5)
c) 3.6cos(3x-2t+3π/7)
d) 4.63cos(3x-2t+3π/5)
Answer: b
Clarification: y = y1 + y2= 2sin(3x-2t) + 3sin(3x-2t+π/4)
= Asin(3x-2t+φ).
A2 = A12 + A22 + 2A1A2cosθ, where θ = π/4, A1 = 2 & A2 = 3.
∴ A = sqrt(4+9+12/√2) = 4.63m.
Tanφ = A2sinθ / (A1 + A2cosθ)
= (3/√2)/(2+3/√2) = 0.51. ∴ φ = 27rad.
∴ y = 4.63sin(3x-2t+8.6π) = 4.63sin(3x-2t+3π/5).

2. A wave having an amplitude of 3cm is to be superimposed with another wave of the same amplitude. What should be their phase difference if the net amplitude has to be 0?
a) π/2
b) π
c) 2π
d) 0
Answer: b
Clarification: The net amplitude is given by: A2 = A12 + A22 + 2A1A2cosθ,
where θ is the phase difference.
For A to be zero 9 + 9 + 2(9)(9)cosθ = 0
∴ θ = π.

3. If the two pulses of equal amplitude have 2J of energy each, what will be the energy of the system when they overlap with each other making the string entirely straight?

a) 0
b) 4J
c) 2J
d) 1J
Answer: b
Clarification: When the two pulses overlap, the string will become straight and the total energy will be in the form of kinetic energy.
As energy will be conserved, energy at that instant = 2+2 = 4J.

4. In superposition of waves the displacements get added like vectors. True or False?
a) True
b) False
Answer: a
Clarification: When waves interfere, the resultant displacement is given by vector addition of their individual displacements.

250+ TOP MCQs on Measurement of Mass | Class 11 Physics

Physics Multiple Choice Questions on “Measurement of Mass”.

1. Which of the following is the standard unit of measurement of mass?
a) Gram
b) Kilogram
c) Pound
d) Dozen
Answer: b
Clarification: Kilogram is the standard unit of measurement of mass. Pound and gram are also units of mass nut are not standard. Dozen is a unit of measurement of quantity.

2. Which of the following is the correct relation?
a) 1 Kg = 100 g
b) 1 Kg = 1 g
c) 1 g = 0.001 Kg
d) 1 g = 0.01 Kg
Answer: c
Clarification: 1 kilogram consists of a thousand grams. Therefore 1 Kg = 1000g, which is equivalent to 1g = 0.001 Kg.

3. Mass can be explained as _____
a) Amount of space
b) Amount of time
c) Amount of weight
d) Amount of matter
Answer: d
Clarification: Mass is the amount of matter in a body. Amount of space covered by a body is called volume. Amount of time and weight do not have any physical significance.

4. Mass can be measured using _____
a) Beam balance
b) Clock
c) Our hands
d) Water
Answer: a
Clarification: Mass is usually measured using a beam balance. In a bean balance, we put a weigh an unknown mass against a known mass. This is the most common method of mass measurement.

5. Mass is a _____
a) Scalar quantity
b) Vector quantity
c) Free quantity
d) Dependent quantity
Answer: a
Clarification: Mass is a scalar quantity. This means that it does not have direction. Scalar quantities are also called as directionless quantities.

6. Weight represents ___
a) Mass
b) Time
c) Pressure
d) Force
Answer: d
Clarification: Weight is the force exerted on a body by gravity. It is the quantification of the gravitational pull on a body. Weight is equal to mass times the acceleration due to gravity.

7. Which one of the following units can be used to measure matter?
a) Kilogram
b) Newton
c) Second
d) Mile
Answer: a
Clarification: Mass is used to measure matter. Hence, the units to measure matter are same as the ones used to measure mass. Among the available choices, kilogram can be used to measure mass. Therefore, kilogram can be used to measure matter.