cbse 11th physics | Online Objective Test

Q2. For solids near room temperature the molar specific heat (R is the universal gas constant)

A. 5R

B. 3R

C. 2R

D. R

Answer : Option B
Explaination / Solution:

The molar specific heats of solids also demonstrate a marked temperature dependence. Solids have molar specific heats that generally decrease in a nonlinear manner with decreasing temperature and approach zero as the temperature approaches absolute zero. At high temperatures (usually above 300 K), the molar specific heats approach the value of 3R ≈ 25 J/mol.K, a result known as the DuLong–Petit law.

Physical World Prepare / Learn

Q3. The microscopic domain of physics deals with

A. the constitution and structure of matter at the scales of stars and planets and their interaction with different elementary particles

B. None of these

C. The constitution and structure of matter at the scales of atoms and nuclei and their interaction with different elementary particles

D. the constitution and structure of matter at the scales of atoms and nuclei and their interaction with different bodies on the earth

Answer : Option C
Explaination / Solution:

Microscopic domain includes atomic,molecular and nuclear phenomena. It can be said as the study of matter.It includes the study of structure and configuration of atom,nucleus and the constitute particles of atom-electron,proton,neutron and interaction with elementary particles like electron,photon etc.

Laws of Motion Prepare / Learn

Q4. Impulse is a

A. vector and equals the change of mass

B. scalar and equals the change of mass

C. vector and equals the inertia of momentum

D. vector and equals the change of momentum

Answer : Option D
Explaination / Solution:

Since force is a vector quantity, impulse is also a vector in the same direction.

Impulse J produced from time t1 to t2 is defined to be

$J = \int_{t_{1}}^{t_{2}} F d t$

where F is the resultant force applied from t1 to t2

force is related to momentum p by

F = dp/dt

therefore,

$\begin{aligned} J & = \int_{t_{1}}^{t_{2}} \frac{d p}{d t} d t \\ = \int_{p_{1}}^{p_{2}} d p \\ = p_{2} - p_{1} = Δ p \end{aligned}$

where $Δ p$ is the change in linear momentum from time t1 to t2

Mechanical Properties of Fluids Prepare / Learn

Q5. Flow is said to be steady if

A. the flow rate does not change with time

B. the flow rate increases with time

C. the flow rate decreases 10% every second

D. the flow rate decreases 20% every second

Answer : Option A
Explaination / Solution:

The flow velocity u of a fluid is a vector field $u = u (x, t)$

which gives the velocity of an element of fluid at a position x and time t.

The flow of a fluid is said to be steady if u does not vary with time. That is if $\frac{δ u}{δ t} = 0.$

Kinetic Theory Prepare / Learn

Q6. The average kinetic energy of a molecule

A. is proportional to the absolute temperature of the gas

B. is not dependent on absolute temperature of the gas

C. is inversely proportional to the molecular mass of the gas

D. is inversely proportional to the absolute temperature of the gas

Answer : Option A
Explaination / Solution:

E=32kT

E∝T

Thermal Properties of Matter Prepare / Learn

Q7. Which of these materials has low coefficient of volume expansion αV ?

A. pyrex glass

B. paraffin

C. water

D. alcohol

Answer : Option A
Explaination / Solution:

Glass is a ceramic material made from silica.So that it has lower coefficient of volume expansion in comparison to metal and liquid.

Units and Measurements Prepare / Learn

Q8. Absolute error of the measurement is

A. the difference between two individual measurements and their mean

B. the difference between the individual measurement and the true value of the quantity

C. the difference between the individual measurement and the true value of the quantity cubed.

D. the difference between the individual measurement and the true value of the quantity squared.

Answer : Option B
Explaination / Solution:

Absolute error is defined as the magnitude of difference between the actual and the individual values of any quantity in question.

Say we measure any given quantity for n number of times and a1 , aa2 , aa3 ….. an are the individual values then Arithmetic mean

am =( [a1+a2+a3+ ….. + an]/n )

Now absolute error formula as per definition

Oscillations Prepare / Learn

Q9. The time period of a simple pendulum is given by ( l is length of pendulum and g the acceleration due to gravity)

A. T = 2

\sqrt{\frac{l}{g}}

B. T = 4

π

\sqrt{\frac{l}{g}}

C. T = 2

π

\sqrt{\frac{l}{g}}

D. T =

π

\sqrt{\frac{l}{g}}

Answer : Option C
Explaination / Solution:
No Explaination.

Gravitation Prepare / Learn

Q10. In Cavendish’s experiment,

A. net force on bar AB having two small lead spheres due to gravitational forces is negative

B. net torque on bar AB having two small lead spheres due to gravitational forces is positive

C. net force on bar AB having two small lead spheres due to gravitational forces is positive

D. torque on bar AB having two small lead spheres due to gravitational forces is balanced by the restoring torque of the wire

Answer : Option D
Explaination / Solution:

Cavendish's apparatus for experimentally determining the value of G involved a light, rigid rod about 2-feet long. Two small lead spheres were attached to the ends of the rod and the rod was suspended by a thin wire. When the rod becomes twisted, the torsion of the wire begins to exert a torsional force that is proportional to the angle of rotation of the rod. The more twist of the wire, the more the system pushes backwards to restore itself towards the original position.

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