Class 9-Physics GravitationContact Number: 9667591930 / 8527521718

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Inverse square law means

1. $\propto r$

2. $\propto {r}^{-1}$

3. $\propto {r}^{-2}$

4. $\propto \frac{1}{{r}^{3/2}}$

An astronaut in the prbit in a spacecraft fells weightlessness

1. due to the absence of gravity inside

2. due to the fact that spacecraft has no energy

3. because acceleration in the orbit is equal to acceleration of gravity of gravity outside

4. there is no gravity outside

Gravitational force is a

1. weakest force

2. strongest force

3. short-range force

4. non-central force

Newton's law of gravitation is valid

1. in laboratory

2. only on the earth

3. only in our solar system

4. everywhere

If ${\mathrm{m}}_{\mathrm{e}}$ is the mass of a body on the surface of the earth and ${\mathrm{m}}_{\mathrm{m}}$ is the mass of the same body on the moon then

1. ${\mathrm{m}}_{\mathrm{e}}=6{\mathrm{m}}_{\mathrm{m}}$

2. ${\mathrm{m}}_{\mathrm{e}}<{\mathrm{m}}_{\mathrm{m}}$

3. ${\mathrm{m}}_{\mathrm{e}}>{\mathrm{m}}_{\mathrm{m}}$

4. ${\mathrm{m}}_{\mathrm{e}}={\mathrm{m}}_{\mathrm{m}}$

Where will it be profitable to purchase one kilogram sugar?

1. At poles

2. At equator

3. At ${45}^{\xb0}$ latitude

4. At ${40}^{\xb0}$ latitiude

The weight of a body of mass 5 kg is

1. 69.0 N

2. 79.0 N

3. 49.0 N

4. 39.0 N

The mass of a body is measured to be 12 kg on the earth. If it is taken to moon, its mass willbe

1. 12 kg

2. 72 kg

3. 10 kg

4. 2 kg

A mass of a body is measured to be 12 kg on the earth. If it is taken to moon, its mass will be

1. 12 kg

2. 72 kg

3. 10 kg

4. 2 kg

The earth attracts the moon with a gravitational force of ${10}^{20}$ N. Then the moon attracts the earth with the gravitational force of

1. ${10}^{-20}\mathrm{N}$

2. ${10}^{2}\mathrm{N}$

3. ${10}^{20}\mathrm{N}$

4. ${10}^{10}\mathrm{N}$

When an object is thrown upward, the force of gravity is

1. opposite to the diection of motion

2. in the same direction as the direction of motion

3. becomes zero at the highest point

4. increases as it rises up

The earth attacks a body of mass 1 kg on its surface with a force of

1. 1 N

2. $6.67\times {10}^{-11}N$

3. 9.8 N

4. $\frac{1}{9.8}$N

When you put an object on a spring balance, what do you measure?

1. Weight

2. Force

3. Mass

4. Acceleration

The acceleration due to gravity

1. has the same value everywhere in space

2. has the same value everywhere on the earth

3. varies with the latitude on the earth

4. is greater on the moon due to its smaller diameter

A ball is thrown up, the value of g will be

1. zero

2. positive

3. negative

4. negligible

The value of G was first determined experimentally by

1. Newton

2. Henry Cavendish

3. Kepler

4. Galileo

The SI unit of G is

1. $\mathrm{m}{\mathrm{s}}^{-1}$

2. $\mathrm{m}{\mathrm{s}}^{-1}$

3. N

4. ${\mathrm{m}}^{2}{\mathrm{kg}}^{2}$

Which of the following statement is true?

1. g is same at all places on the surface of earth

2. g has its maximum value at the equator

3. g is less at the earth's surface than at a height above it or a depth below it.

4. g is greater at the poles than at the equator.

The gravitational pull exerted by the earth on a body is called

1. true weight

2. gravitational mass

3. apparent weight

4. inertial mass

Two bodies A and B masses 100 g and 200 g respectively are dropped near the earth's surface. Let the acceleration of A and B be ${\mathrm{a}}_{1}\mathrm{and}{\mathrm{a}}_{2}$ respectively. Then

1. ${\mathrm{a}}_{1}={\mathrm{a}}_{2}$

2. ${\mathrm{a}}_{1}<{\mathrm{a}}_{2}$

3. ${\mathrm{a}}_{1}>{\mathrm{a}}_{2}$

4. ${\mathrm{a}}_{1}\ne {\mathrm{a}}_{2}$

An apple falls towards the earth because the earth attracts it . The apple also attracts the earth by the same force. Why do we not see the earth rising towards the apple?

1. Acceleration of the earth is very large when compared to that of apple.

2. acceleration of the earth is equal to that of apple.

3. acceleration of the earth is neither high nor too low.

4. Acceleration of the earth is very small when compared to that of apple.

The value of G depends on

1. mass of the bodies

2. distance between the bodies

3. some other masses kept nearby

4. none of these

According to Kepler's law the relationship between T (time period of revolution of a planet) an d r (the semi-major axis of ellipse) is

1. ${\mathrm{T}}^{2}\propto \mathrm{r}$

2. ${\mathrm{T}}^{2}\propto \mathrm{r}2$

3. ${\mathrm{T}}^{2}\propto {\mathrm{r}}^{-3}$

4. $\mathrm{T}\propto {\mathrm{r}}^{3/2}$

The value of acceleration due to gravity at the Mount

everest is

1. g

2. >g

3. <g

4. zero

As a body is moved from the center of the earth to a height from the surface of the earth

1. the weight if the body first increases from zero to a certain value and then starts decreasing.

2. the weight of the body goes on increasing

3. the weight of the body goes on decreasing

4. the weight of the body first decreases and then increases

The weight of an object

1. increases when taken from the pole to the equator

2. increases when taken from the equator to the pole

3. increases when taken from Delhi to the top of Mount Everest

4. increases when taken from the surface of the earth to moon

The value of g is zero

1. at the top of the atmosphere

2. at 20 km below the surface of the earth

3. at 20 km above the surface of the earth

4. at the center of the earth

Choose the correct statement

1. Weight is a vector quantity

2. The weight of a body in interplanetary space is maximum

3. Weight increases when the bodies go up.

4. 1 N=1 kg $\times $ 1 m ${\mathrm{s}}^{-1}$

If ${\mathrm{G}}_{\mathrm{e}}$ is the value of universal gravitational constant at the earth and ${G}_{m}$ is the value of universal gravitational constant on the moon then

1. ${\mathrm{G}}_{\mathrm{e}}=6{\mathrm{G}}_{\mathrm{m}}$

2. ${\mathrm{G}}_{\mathrm{e}}<{\mathrm{G}}_{\mathrm{m}}$

3. ${\mathrm{G}}_{\mathrm{e}}>{\mathrm{G}}_{\mathrm{m}}$

4. ${\mathrm{G}}_{\mathrm{e}}={\mathrm{G}}_{\mathrm{m}}$

Two masses m and M are kept at a distance r. The ratio of the force exerted on m due to M and that of M due to m is equal to

1. $\frac{\mathrm{m}}{\mathrm{M}}$

2. $\frac{\mathrm{M}}{\mathrm{m}}$

3. $\frac{\mathrm{mr}}{\mathrm{M}}$

4. 1:1

An iron block was weighted at equator and its value was found to be 1 N. When the same iron block is weighed at poles, its value is found to be x N. Then

1. 1=x

2. 1>x

3. x>1

4. can't say

The type force that exists between two charges bodies is

1. only gravitational

2. only electrostatic

3. neither (a) nor (b)

4. both (a) and (b)

Gravitational force is a

1. repulsive force

2. action at a distance force

3. neither (a) nor (b)

4. both (a) and (b)

If R is the radius of the earth, the height at which the weight of a body becomes 1/4 its weight on the surface of the earth is

1. 2R

2. R

3. $\frac{\mathrm{R}}{2}$

4. $\frac{\mathrm{R}}{4}$

If the diameter of the earth becomes two tomes its present value and its mass remains unchanged, then how would the weight of an object on the surface of the earth be affected?

1. Weight would become one-third

2. Weight would become one-fourth

3. Weight would become one-fifth

4. Weight would become one-sixth

Which of the following graphs correctly represents the variation of g on earth?

A simple pendulum has a time period ${\mathrm{T}}_{1}$ when on the earth's surface, and ${\mathrm{T}}_{2}$ when taken to a height R above the earth's surface, where R is the radius od the earth. The value of $\frac{{\mathrm{T}}_{2}}{{\mathrm{T}}_{1}}$ is

1. 1

2. $\sqrt{2}$

3. 0.5

4. 2

Two body of masses 2 kg and 8 kg are seperated by a distance of 9 m. Then the point where the resultant gravitational field is zero is at a distance of

1. 6 m from 8 kg

2. 3 m from 8 kg

3. 6 m from 2 kg

4. 4.5 m from each masses

A body falls through a distance h in certain time on the earth. Then if the same body is related on another planet having mass and radius twice as that of the earth, the distance through which it falls in the same time is

1. h/2

2. 2h

3. h

4. 4h

Suppose we have taken a stone to the center of the earth

1. its weight becoes zero

2. its weight increases

3. its weight is unaffected

4. its mass increases

The weight of an object

1. is the gravity of the matter it contains

2. refers to its inertia

3. is the force with which it is attracted towards the earth

4. is the same as its mass but expressed in different units

Communication satellites moves in the orbits of radius 44400 km around the earth. The acceleration of such a satellite assuming that the only force acting on it is that due to the earth is $({\mathrm{M}}_{\mathrm{e}}=6\times {10}^{24}\mathrm{kg})$

1. $0.4\mathrm{m}{\mathrm{s}}^{-2}$

2. $0.6\mathrm{m}{\mathrm{s}}^{-2}$

3. $0.2\mathrm{m}{\mathrm{s}}^{-2}$

4. $0.1\mathrm{m}{\mathrm{s}}^{-2}$

A stone is dropped from the top of a tower. Its velocity after it had fallen 20 m is

1. $-10\mathrm{m}{\mathrm{s}}^{-1}$

2. $10\mathrm{m}{\mathrm{s}}^{-1}$

3. $-20\mathrm{m}{\mathrm{s}}^{-1}$

4. $20\mathrm{m}{\mathrm{s}}^{-1}$

A balloon of mass m is rising with an acceleration a. A fraction of its mass is detached from the balloon. Its acceleration will

1. decrease

2. increase

3. remain the same

4. none of these

At a place, value of g is less by 1% than its value on the surface of the earth (Radius of earth, R-6400 km). The place is

1. 64 km below the surface of the earth

2. 64 km above the surface of the earth

3. 30 km above the surface of the earth

4. 32 km below the surface of the earth

If the radius of the earth were to be increased by a factor of 3, by what factor would its density have to be changed to keep g the same?

1. 3

2. $\frac{1}{3}$

3. 6

4. $\frac{1}{6}$

A coin and a feather are dropped together in a vacuum. Then

1. the coin will reach the ground first

2. the feather will reach the ground first

3. both will reach the ground at the same time

4. the feather will not fall down

The unit of $\frac{G}{g}$ is

1. $\mathrm{kg}{\mathrm{m}}^{-1}$

2. $\mathrm{kg}{\mathrm{m}}^{-2}$

3. ${\mathrm{m}}^{2}{\mathrm{kg}}^{-1}$

4. $\mathrm{m}{\mathrm{kg}}^{-1}$

If the distance between two bodies becomes 6 times theoretical distance, then the force between them becomes

1. 36 times

2. 6 times

3. 12 times

4. $\frac{1}{36}$ times

The gravitational force between two masses kept in air at a certain distance is x N. The same two masses are now kept in water and the distance between them are same. The gravitational force between these masses in water is y N. Then

1. x=y

2. x<y

3. x>y

4. can't say

If the value of G on the surface of earth is $6.673\times {10}^{-11}N{m}^{2}k{g}^{-2}$, then the value of G on the planet Jupiter is

1. $12\times 6.673\times {10}^{-11}N{m}^{2}k{g}^{2}$

2. $\frac{6.673}{12}\times {10}^{-11}N{m}^{2}k{g}^{-2}$

3. $6.673\times {10}^{-11}N{m}^{2}k{g}^{-2}$

4. $\frac{6.673}{6}\times {10}^{-11}N{m}^{2}k{g}^{-2}$

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