cbse 11th physics | Online Objective Test

Q1.

Consider the cyclic process depicted in Figure if $Δ E_{i n t}$ is negative for the process CA, what are the signs of Q and W are associated with CA?

A. -, 0

B. -, -

C. +, 0

D. -, +

Answer : Option B
Explaination / Solution:

$W = P Δ V = - v e (i n C o m p r e s s i o n Δ V = - v e)$

$\begin{aligned} Δ Q = Δ E_{i n t} + W \\ Δ E_{i n t} = - v e \\ W = - v e \\ s o t h a t Δ Q = - v e \end{aligned}$

Laws of Motion Prepare / Learn

Q2. A stone of mass 0.25 kg tied to the end of a string is whirled round in a circle of radius 1.5 m with a speed of 40 rev./min in a horizontal plane. What is the tension in the string?

A. 6.6 N

B. 6.1 N

C. 6.9 N

D. 6.3 N

Answer : Option A
Explaination / Solution:

Let, m=0.25 kg, r= 1.5m and f= 40 rev/min = 40 rev /60 s= 2/3 rps

ω = 2 π f = 2 π \times \frac{2}{3} = \frac{4 π}{3} r a d s^{- 1}

Tension in the string = Centripetal force

so, $T = m r ω^{2} = 0.25 \times 1.5 \times (\frac{4 π}{3})^{2} = 6.6 N$

Work Energy and Power Prepare / Learn

Q3. In which of the following cases is the work done positive?

A. Work done by gravitational force while a man in lifts a bucket out of a well by means of a rope tied to the bucket

B. Work done by friction on a body sliding down an inclined plane

C. work done by an applied force on a body moving on a rough horizontal plane with uniform velocity

D. Work done by the resistive force of air on a vibrating pendulum in bringing it to rest.

Answer : Option C
Explaination / Solution:

When a body is moving on a rough horizontal surface then their will be 2 forces acting on the body 1. Applied force ( in the direction of motion) 2. friction ( opposite to direction of motion) As applied force is in same direction as displacement so work done will be positive.

System of Particles and Rotational Motion Prepare / Learn

Q4.

Three thin uniform rods each of mass M and length L are placed along the three axis of a Cartesian coordinate system with one end of each rod at the origin. The M.I. of the system about z- axis is

M L^{2}

M L^{2}

(2/3)ML2

M L^{2}

M L^{2}

M L^{2}

M L^{2}

Answer : Option B
Explaination / Solution:

Moment of inertia about an axis passing through edge

$I = \frac{M L^{2}}{3}$

Moment of inertia of system about z-axis

$\begin{aligned} I = I_{x} + I_{y} + I_{z} \\ I = \frac{M L^{2}}{3} + \frac{M L^{2}}{3} + 0 \\ I = \frac{2}{3} M L^{2} \end{aligned}$

Mechanical Properties of Fluids Prepare / Learn

Q5. Soldering of two metals possible because of the property of

A. viscosity

B. surface tension

C. osmosis

D. cohesion

Answer : Option D
Explaination / Solution:
No Explaination.

Physical World Prepare / Learn

Q6. The law of conservation of energy is.

A. is valid only for Newtonian mechanics

B. thought to be valid across all domains of nature, from the microscopic to the macroscopic

C. is valid only for relativistic mechanics

D. is valid only for applied mechanics

Answer : Option B
Explaination / Solution:

The law of conservation of energy is thought to be valid across all domains of nature, from the microscopic to the macroscopic. It is routinely applied in the analysis of atomic, nuclear and elementary particle processes. At the other end. all kinds of violent phenomena occur in the universe all the time. Yet the total energy of the universe (the most ideal isolated system possible!) is believed to remain unchanged.

Kinetic Theory Prepare / Learn

Q7. One mole of an ideal monatomic gas is at an initial temperature of 300 K. The gas undergoes an isovolumetric process, acquiring 500 J of energy by heat. It then undergoes an isobaric process, losing this same amount of energy by heat. Determine the new temperature of the gas

A. 316 K

B. 301 K

C. 343 K

D. 333 K

Answer : Option A
Explaination / Solution:

for monoatomic gas CV = 1.5R, CP = 2.5R

At const volume,

Q = 500 J

$\begin{aligned} Q = n C_{V} Δ T \\ 500 = 1 \times 1.5 \times 8.31 (T_{1} - 300) \\ T_{1} = 340 K \end{aligned}$

At const pressure Q = 500 J

$\begin{aligned} Q = n C_{P} Δ T \\ 500 = 1 \times 2.5 \times 8.31 (340 - T_{2}) \\ T_{2} = 316 K \end{aligned}$

Thermal Properties of Matter Prepare / Learn

Q8. In an insulated vessel, 250 g of ice at 0

^{\circ}

C is added to 600 g of water at 18.0

^{\circ}

C. How much ice remains when the system reaches equilibrium?

A. 87 g

B. 134 g

C. 114 g

D. 94 g

Answer : Option C
Explaination / Solution:
No Explaination.

Units and Measurements Prepare / Learn

Q9. Horse power is unit of

A. Current

B. Power

C. Time

D. Distance

Answer : Option B
Explaination / Solution:

The horsepower (hp) is a unit in the foot-pound-second ( fps ) or English system, sometimes used to express the rate at which mechanical energy is expended. It was originally defined as 550 foot-pounds per second (ft-lb/s). A power level of 1 hp is approximately equivalent to 746 watt.

Oscillations Prepare / Learn

Q10. A weightless spring which has a force constant k oscillates with frequency n when a mass m is suspended from it. The spring is cut into two equal halves and a mass 2m is suspended from it. The frequency of oscillation will now become

A. 2n/

\sqrt{2}

D. n/

\sqrt{2}

Answer : Option D
Explaination / Solution:
No Explaination.

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