Gravitation - Online Test

Answer : Option B
Explaination / Solution:

A polar orbiting satellite closely parallels the earth's meridian lines. It passes over the north and south poles each revolution. As the earth rotates to the east beneath the satellite, each pass monitors an area to the west of the previous pass at intervals of roughly 90 to 100 minutes. These strips can be pieced together to produce a picture of a larger area.They are used in monitoring the weather, observing the Earth’s surface, military uses including spying.

Answer : Option A
Explaination / Solution:

The acceleration due to gravity due to a body at point P on the surface of earth is

g=GMR2    -(1)

Let the body is placed to point Q at a height h abovr the surface of earth, then acceleration due to gravity:

gh=GM(R+h)2  -(ii)

Dividing (i) & (ii), we get

ghg=R2(R+h)2$\frac{g_h}{}$

By simplifying and expanding through binomial theorem, we get

gh=g(1−2hR)

From above expression we can clearly say that with increase in altitiude h , the value of acceleration due to gravity decreases.

Answer : Option A
Explaination / Solution:

The escape velocity is the minimum velocity required to leave a planet or moon. For a rocket or other object to leave a planet, it must overcome the pull of gravity.

Vescape=2GMR−−−−√

Vescape=11184 m/sec approximate to 11.2 km/sec

Answer : Option A
Explaination / Solution:

Gravitational Force

F=mg

⇒F=5×10.7=53.5 N

Answer : Option B
Explaination / Solution:

Work done=mgh1+hRIf h=R then,⇒Work done=mgh1+RR=12mgh

Answer : Option C
Explaination / Solution:

Escape velocity ve α Rρ−−√and if density remains constant⇒ve α RSo if the radius reduces by 4% then escape velocity also reduces by 4%

Answer : Option D
Explaination / Solution:

Let L be the width of the film. Since the film has two surfaces, the total length along which the surface force acts on the slider is 2L. The surface tension S in the film is defined as the ratio of the surface force F to the length d (perpendicular to the force) along which the force acts

  S=F/d

Hence, in the case, d = 2L

S=F/2L