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OTI365 - NTSE - X Standard
NTSE SAT Physics - Gravitation Important Questions with Answer

SAT Physics - Gravitation

Exam Duration: 45 Mins Total Questions : 30

1 )

Name the fundamental force which holds the planets in their orbits around the sun.

(a)
Gravitational force of attraction
(b)
Electrostatic force of attraction
(c)
Nuclear force of attraction
(d)
Electrostatic force of attraction

2 )

The upward force acting on an object submerged in a liquid is _____

(a)
Thrust
(b)
Buoyant force
(c)
Pressure
(d)
Force of friction

3 )

The normal force per unit area is called _________

(a)
Pressure
(b)
Thrust
(c)
Balanced force
(d)
Pascal

4 )

A satellite of the earth is revolving in a circular orbit with a uniform speed v. If the gravitational force suddenly disappears, the satellite will :

(a)
Continue to move with velocity v along the original orbit
(b)
Fall down with increasing velocity
(c)
Move with a velocity v tangentially to the original orbit
(d)
Ultimately come to rest somewhere on the original orbit

5 )

Weightlessness experienced while orbiting the earth in spaceship, is the result of.

(a)
Inertia
(b)
Zero gravity
(c)
Acceleration
(d)
Free fall towards earth

6 )

Mass per unit volume of a substance is called

(a)
Density
(b)
Relative density
(c)
Specific gravity
(d)
None

7 )

The period of geostationary artificial satellite is

(a)
24 hours
(b)
6 hours
(c)
12 hours
(d)
48 hours

8 )

A satellite is revolving around the sun in a circular orbit with uniform velocity v. If the gravitational force suddenly disappears, the velocity of the satellite will be

(a)
Zero
(b)
v
(c)
2v
(d)
Infinity

9 )

Two objects of different masses falling freely near the surface of moon would

(a)
have same velocities at any instant
(b)
have different accelerations
(c)
experience forces of same magnitude
(d)
undergo a change in their inertia

10 )

The value of acceleration due to gravity

(a)
is same on equator and poles
(b)
is least on poles
(c)
is least on equator
(d)
increases from pole to equator

11 )

The gravitational force between two objects is F. If masses of both objects are halved without changing distance between them, then the gravitational force would become

(a)
F/4
(b)
F/2
(c)
F
(d)
2F

12 )

An object is put one by one in three liquids having different densities. The object floats with 1/9, 2/11 and 3/7 parts of their volumes outside the liquid surface in liquids of densities d₁, d₂ and d₃ respectively. Which of the following statement is correct?

(a)
d₁> d₂> d₃
(b)
d₁> d₂< d₃
(c)
d₁< d₂> d₃
(d)
d₁< d₂< d₃

13 )

In the relation F = G M m/d², the quantity G

(a)
depends on the value of g at the place of observation
(b)
is used only when the earth is one of the two masses
(c)
is greatest at the surface of the earth
(d)
is universal constant of nature

14 )

The weight of an object at the centre of the earth of radius R is

(a)
zero
(b)
infinite
(c)
R times the weight at the surface of the earth
(d)
1/R² times the weight at surface of the earth

15 )

An object weighs 10N in air. When immersed fully in water, it weighs only 8 N. The weight of the liquid displaced by the object will be

(a)
2N
(b)
8N
(c)
10N
(d)
12N

16 )

If the mass of a body is M on the surface of the earth, then its mass on the surface of the moon will be

(a)
M/6
(b)
M
(c)
M+6
(d)
zero

17 )

Weight

(a)
is a vector quanity
(b)
of a body in Interplanetary space is maximum
(c)
increases when the bodies go up
(d)
none of these

18 )

The value of g near the earth's surface is

(a)
8.9 m/s²
(b)
8.9 m/s
(c)
9.8 m/s²
(d)
9.8 m/s

Solution :

A geostationary satellite

19 )

A geostationary satellite

(a)
moves faster than the near earth satellite
(b)
has a time period less that of a near earth satellite
(c)
revolves about the polar axis
(d)
is stationary is space

20 )

1 kg wt is equal to

(a)
980 dynes
(b)
9.80 dynes
(c)
98 dynes
(d)
none of these

21 )

The escape velocity for a rocket on the earth is 11.2km/s. Its value on a planet where acceleration due to gravity is twice that on the earth and the diameter of the planet is twice that of the earth, will be (in Km/s

(a)
11.2
(b)
5.6
(c)
22.4
(d)
33.6

22 )

The escape velocity from the earth's surface is 11.2 km/s. If the radius of a planet is double to that of the earth but the average density is same as that of the earth, then the average density is same as of the earth then the escape velocity from the planet would be

(a)
22 km/s
(b)
11 km/s
(c)
5.5 km/s
(d)
15.5 km/s

23 )

Given that there is a relationship between the orbital radius of a planet and its period of revolution and that the period of Mercury, Earth, Jupiter and Neptune are nearly 0.24, 1, 11.8 and 165 years. It follow that the period of revolution of

(a)
Venus is less than 0.24 years
(b)
Mars is less than 12 years
(c)
Uranus is more than 165 years
(d)
Uranus is less than 165 years but more than 12 years

24 )

A geo-stationary satellite is orbiting around earth at height of 30,000 km in circular orb~. The radius of the earth is taken as 6000 km. The geo-stationary satellite comes back to its position after one revolution in exactly 24 hours. Let the acceleration due to gravity (g) be 10 m/s? and mass of satellite be 1000 kg calculate the work done in 12 hours when moving under gravitational force.

(a)
3.6π x 10¹⁴ J
(b)
2π x 7.2π x 10¹⁴ J
(c)
1.8π x 10¹⁴J
(d)
0J

25 )

The time period of a satellite revolving in a circular orbit of radius R is T. Time period of another satellite revolving in the circular orbit of radius 4R will be

(a)
4T
(b)
T/4
(c)
8T
(d)
T/8

26 )

Two artificial satellites of masses m₁ and m₂ (m₁ > m₂) are revolving round the earth in circular orbits of radii r₁ and r₂ (r₁ > r₂) resp. Which of the following statement is true.

(a)
v₁ and v₂
(b)
v₁ > v₂
(c)
v₁ < v₂
(d)
None

27 )

Weight is

(a)
measured by a spring balance
(b)
measured by a beam balance
(c)
measured in kg
(d)
a scakar quantity

28 )

Two metal spheres of equal radius rare touch in each other. The force of attraction F between them is

(a)
F∝ r⁴
(b)
F∝ r⁶
(c)
F∝ r²
(d)
F∝ 1/r⁴

29 )

The value of the acceleration due to gravity at a height of 12,800 km from the surface of the earth (R₄ = 6400 km)g= g \(R^2\over Rh\) is

(a)
3.09 m/s²
(b)
1.09 m/s²
(c)
4.08 m/s²
(d)
5.07 m/s²

30 )

Consider a heavenly body which has a mass twice that of the earth and a radius thrice that of the earth.The weight of a book on this heavenly body, if its weight on the earth is 900 N will be: