# CBSE Class 9th Science 10 – Gravitation MCQs

#### Two bodies A and B are having volumes in the ratio 2 :3. The ratio of the thrusts exerted on them, when the two bodies are immersed in a liquid is ____.

Thrust exerted on a body, F = Vdg As the A and B are immersed in the same liquid, F ∝ V Hence, the ratio of the thrusts exerted on them is 2 : 3

#### If Earth stops rotating around its own axis, the value of acceleration due to gravity at its equator decreases.

The value of acceleration due to gravity (g) at its equator decreases as shown below:
g _{latitude} = g _{pole } − Rω^{2}
where 'R' is the radius of the earth and 'ω' is the angular velocity of the Earth about its own axis.
If Earth stops rotating about its own axis, then its angular velocity is zero and hence the value of 'g' increases.

#### When a planet is moving around the Sun, the time period equation is T = 2πR^{3/2}/√GM, where M represents ____.

When a planet is moving around the Sun, the time period equation is T = 2πR^{3/2}/√GM, where M represents mass of the Sun.
R represents the distance from the Sun to the centre of the planet, where the planet is moving around the Sun.

#### While floating the weight of the body is equal to the up thrust.

While floating the weight of the body is equal to the up thrust.

#### The centripetal force required for the rotation of the Earth around the Sun is provided by the ____ force.

The centripetal force required for the rotation of Earth about the Sun is provided by the gravitational force.

#### A body floats in liquid 'A' but sink in another liquid 'B'. It implies that the density of 'A' is more than that of 'B'.

As the body floats in liquid 'A', its density is less than that of liquid 'A'. Density of a body is more than that of liquid 'B' because it sinks in it. Hence, density of 'A' is more than that of 'B'.

#### The Earth takes ____ to complete one revolution around the Sun.

Earth takes 365 days to complete one revolution around the Sun.

#### The study of fluid includes ____.

The study of fluids includes liquids and gases.

#### The concentration of acid is measured in a battery through a ____.

The concentration of acid is measured in a battery through a hydrometer.

#### The weight of a body is equal to the ____.

The weight of a body is equal to the product of its mass and the acceleration due to gravity at the place.

#### The Heliocentric theory of solar system is proposed by ____.

The Heliocentric theory of solar system is proposed by Nicolas Copernicus. He showed the world a heliocentric solar system, in which the Sun is at the centre, the Earth and other planets revolve around the Sun in circular orbits.

#### The Kepler's third law is defined as ____.

The square of the time period of revolution of a planet around the Sun is directly proportional to the cube of the length of the semi-major axis of the elliptical orbit.
⇒ T^{2 }∝ R^{3}

#### A toy balloon filled with CO_{2} will rise to the ceiling.

CO_{2} balloon has more density than air, hence it will fall to the bottom.

#### A planet revolves around the Sun in such a way that it's areal velocity ____.

According to Kepler's second law, the line joining the Sun to the planet sweeps out equal areas in equal interval of time i.e., the areal velocity of the planet around the Sun is constant. Areal velocity = dA /dt = constant.

#### A body is floating in a liquid container. Which of the following is the correct equation? (F_{g} is gravitational force on body, F_{b} is buoyant force on the body).

When a body is floating in a liquid container, F_{g} = F_{b} where, F_{g} is gravitational force on body and F_{b} is buoyant force on the body.
Therefore, F_{g} and F_{b} have equal magnitudes but they act in opposite directions.

#### The basic concept in pressure cooker is to cook food, at high temperature and pressure in relatively less time.

At high pressure, boiling point of water increases, as a result food is cooked quickly in pressure cooker.

#### The relation between 'g' and 'G' is given by g = GM/ r^{2}

The relation between 'g' and 'G' is given by, g = GM/ r^{2}

#### The magnitude of force applied by the Earth on the Moon is greater than the force applied by the Moon on the Earth.

The gravitational attractive force of the earth on the moon is action force then the attractive force of the moon on the earth is a reaction force. Action reaction forces are equal in magnitude and opposite in direction. Hence, the magnitude of force applied by the Earth on the Moon is equal to the force applied by the Moon on the Earth. That means, the given statement is false.

#### The second law of Kepler's is also known as ____.

The second law of Kepler's states that a line drawn from the Sun to the planet sweeps out equal areas in equal intervals of time i.e., the areal velocity of the planet around the Sun is constant. Areal velocity = dA/dt = a = constant.

#### The measurement of the atmospheric pressure was first made by ____.

The measurement of atmospheric pressure was first made by Torricelli.

#### Which of the following is the correct unit of acceleration due to the gravity in CGS system?

The unit of acceleration due to gravity in CGS system is cm/ s^{2}.

#### One bar is equal to ____ Pa.

One bar is equal to 10^{5} Pa.

#### A block of wood is floating in a lake. The apparent weight of the floating block is ____.

For a floating block, up thrust is equal to the weight of the block. Hence, apparent weight will be zero.

#### Pressure at a point in a liquid does not depend upon the ____.

As, P = hdg, pressure does not depend upon the area of the container.

#### When air is removed from a can, the can gets squeezed.

When air is removed from a can, it gets squeezed due to the force exerted by atmospheric pressure on it.

#### Acceleration due to gravity is a scalar quantity.

Acceleration due to gravity has both magnitude as well as direction. So, it is a vector quantity.

#### The weight of a body at the centre of the Earth is zero.

The value of acceleration due to gravity at the centre of the Earth is zero. Hence, the weight of a body at the centre of the Earth is zero.

#### The value of 'G' on Earth is greater than the value of 'G' on Jupiter.

The value of 'G' is constant, irrespective of the types of planets.

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