CBSE 11TH PHYSICS - Online Test

Answer : Option C
Explaination / Solution:

If there is a satellite in the equatorial plane rotating in the direction of earth’s rotation from west to east, then for an observer, on the earth, angular velocity of satellite will be (ωs−ωE)

The time interval between the two consecutive appearances overhead will be,

T=2πωs−ωE=TsTETE−Ts      

If ωs=ωE, T = ∞, i.e. satellite will appear stationary relative to earth. Such satellites are called geostationary satellites and will have a period of rotation as the period of rotation of earth i.e  24 Hrs.

Answer : Option C
Explaination / Solution:

initial velocity u = 60 m/s

As it stop final velocity v = 0

Time taken t = 4 s

We know,

a=v−ut

=0−604=−15 m/s2

Negative sign shows it is declaration.

Answer : Option B
Explaination / Solution:
No Explaination.

Answer : Option D
Explaination / Solution:

Work is defined as a dot-product (or scalar product) of force and displacement, both of which are vectors. A scalar (dot) product of two vectors gives a scalar result.

Answer : Option B
Explaination / Solution:

If external force is absent then linear momentum of system remains conserved. In collision force of impact due to collision is internal and very large.

Answer : Option B
Explaination / Solution:

We know that Yield strength times the Area give the weight of the body.

As Yield strength = weight of body/area

For safety purposes

Yield strength ≥ weight of body/area 

Sy${\mathrm{S}}_{\mathrm{y}}$ ≥ Mg/A

A ≥ Mg/ Sy

Answer : Option D
Explaination / Solution:

The performance of refrigerator is expressed by means of cofficient of performance

cofficient of performance  = Heat extracted / work done = Q2W

Answer : Option B
Explaination / Solution:

The force acting on a coin is due to gravitational force which causes an acceleration in downward direction.

Answer : Option A
Explaination / Solution:

As no external fields like, electric,magnetic and gravitational field acting on electron the net force is zero

Answer : Option D
Explaination / Solution:

In science, a hypothesis is an idea or explanation that you then test through study and experimentation.