CBSE 11TH PHYSICS - Online Test

Q1. The direction of the universal gravitational force between particles of masses m1 and m2 is:

A. towards

m_{2}

B. towards

m_{2}

m_{1}

and towards

m_{1}

m_{2}

towards the center of the earth

D. towards

m_{1}

Answer : Option B
Explaination / Solution:

since gravitational force is attractive in nature, so if there are two particles of m1 & m2 .

So One Force will be on m1 which will be directed towards m 2. i.e ${\vec{F}}_{12} = G \frac{m_{1} m_{2}}{{r_{21}}^{2}}$

And other force wiil be on m2 which will be directed towards m 1 i.e ${\vec{F}}_{21} = - G \frac{m_{1} m_{2}}{{r_{12}}^{2}}$

Clearly, It can be seen that ${\vec{F}}_{12} = - {\vec{F}}_{21}$ Because thsese forces are attracted to each other and direction of each force is opposite to other one.

Motion in A Straight Line Prepare / Learn

Q2. For motion in 3 dimensions we need

A. No frame of reference is required ; a set of 3 points will do.

B. frame of reference consisting of a clock and a Cartesian coordinate system having two mutually perpendicular axes, labeled X-, and Y- axes

C. No frame of reference is required a single point will do.

D. frame of reference consisting of a clock and a Cartesian coordinate system having three mutually perpendicular axes, labeled X-, Y-, and Z- axes

Answer : Option D
Explaination / Solution:

Motion is a change in position of an object with time. In order to specify position, we need to use a reference point and a set of axes. It is convenient to choose a rectangular coordinate system consisting of three mutually perpenducular axes, labelled X-, Y-, and Z- axes. The point of intersection of these three axes is called origin (O) and serves as the reference point. The coordinates (x, y. z) of an object describe the position of the object with respect to this coordinate system. To measure time, we position a clock in this system. This coordinate system along with a clock constitutes a frame of reference.

Waves Prepare / Learn

Q3. in transverse waves, the constituents of the medium

A. oscillate perpendicular to the direction of wave propagation

B. oscillate parallel to the direction of wave propagation

C. oscillate at 40

^{\circ}

to the direction of wave propagation

D. oscillate at 30

^{\circ}

to the direction of wave propagation

Answer : Option A
Explaination / Solution:

In transverse wave motion medium particles oscillates or vibrates in a direction perpendicular to the direction of wave propagation to form crest & trough in the wave motion.

System of Particles and Rotational Motion Prepare / Learn

Q4. the centre of mass of a system of particles moves

A. as if all the mass of the system was concentrated in a sphere around the centre of mass and all the external forces were zero

B. as if all the mass of the system was concentrated at the centre of mass and all the external forces were applied at that point

C. as if all the mass of the system was concentrated at the axis of rotation and all the external forces were absent

D. as if all the mass of the system was concentrated at the centre of mass and all the external forces were zero

Answer : Option B
Explaination / Solution:

The centre of mass of a system of particles moves as if all the mass of the system is concentrated at the centre and all the external forces were applied at that point. In order to ease the calculations involved in the dynamics of an extended body, we treat any extended body as the system of particles, and the motion of centre of mass of the system is calculated by taking the mass of the whole system to be concentrated at the centre of mass and the external forces acting on system are said to be acting on the centre of mass.

Work Energy and Power Prepare / Learn

Q5. The work done by the force is defined to be

A. the negative product of component of the force in the direction of the displacement and the magnitude of this displacement

B. the product of force and the magnitude of the displacement

C. the product of component of the force in the direction of the displacement and the magnitude of the displacement

D. the product of component of the force in the direction perpendicular to displacement and the magnitude of the displacement

Answer : Option C
Explaination / Solution:

Work done is given by

W = (Fcos $θ$ )d

here Fcos $θ$ is the component of applied force in direction of displacement and d is magnitude of displacement.

Motion in A Plane Prepare / Learn

Q6.

Multiplying a vector $\vec{v}$ by a negative real number $λ$

λ

A. gives a scalar that is

λ

times the magnitude of

\vec{v}

B. gives a vector

\vec{v^{'}}

λ \vec{v}

in the same direction as

\vec{v}

C. gives a vector

\vec{v^{'}}

λ \vec{v}

in a direction opposite to

\vec{v}

D. gives a scalar that is

λ

times the polar angle of

\vec{v}

Answer : Option C
Explaination / Solution:

If a vector is multiplied by a negative number (for example -2, -3 ,-5, -60 unit etc.) or a scalar not only its magnitude is changed but its direction also reversed.

Mechanical Properties of Solids Prepare / Learn

Q7. The S.I unit of stress is

A. Pascal

B. Joule

C. Newton

D. Watt

Answer : Option A
Explaination / Solution:
No Explaination.

Physical World Prepare / Learn

Q8. A scientific theory is accepted if

A. The theory is approved by a panel of people after studying the theory only

B. The theory is very simple elegant or very complicated

C. predictions of the theory are confirmed by experiments

D. The theory is derivable from other theories logically.

Answer : Option C
Explaination / Solution:

A scientific theory is an explanation of some aspect of the natural world that can, in accordance with the scientific method, be repeatedly tested, using a predefined protocol of observations and experiments.Established scientific theories have withstood rigorous scrutiny and are a comprehensive form of scientific knowledge.

Laws of Motion Prepare / Learn

Q9. Force is a

A. qualitative measure of the interaction between two bodies

B. qualitative measure of the momentum of two bodies

C. quantitative measure of the momentum between two bodies

D. quantitative measure of the interaction between two bodies

Answer : Option D
Explaination / Solution:

Newton's second law of motion gives the quantitative definition of force. The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object

Mechanical Properties of Fluids Prepare / Learn

Q10. The units of pressure in SI system is

A. Newton

B. Joule

C. Watt

D. Pascal

Answer : Option D
Explaination / Solution:

The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N/m2, or kg. m. s−2). This name for the unit was added in 1971; before that, pressure in SI was expressed simply in newtons per square metre

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cbse 11th physics TEST : 9