Gravitation | MCQs

Explanation

Kepler's law explains the motions of planets in the solar system.

Kepler's Laws of Planetary Motion

They describe how:

(1) planets move in elliptical orbits with the Sun as a focus

(2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit

(3) a planet's orbital period is proportional to the size of its orbit (its semi-major axis).

Explanation

The escape velocity of a body in the gravitational field of Earth is primarily dependent on the mass of the Earth and the radius of the Earth.

It does not depend on the mass of the body or the angle at which it is thrown.

The formula for escape velocity 𝑣e is given by:

Explanation

In deep space far from massive objects, the gravitational pull becomes negligible, effectively making gravity zero.

This is why astronauts experience weightlessness in such regions.

Explanation

Near Earth's surface, the acceleration due to gravity is 9.8 m/s2 (32 ft/s2).

This means that, ignoring the effects of air resistance,

the speed of an object falling freely will increase by about 9.8 meters per second (32 ft/s) every second.

Explanation

The earth moves around the sun.

زمین سورج کے گرد گھومتی ہے۔

"The" is used because it refers to a specific object, in this case, "the Earth."

It is a definite article used when speaking about something unique or specific.

Explanation

At the center of the Earth, gravitational forces from all directions cancel out.

Hence, the net gravitational force (and weight) is zero.

Explanation

Explanation

• The formula for the period of a pendulum is T = 2π√(l/g), where l is the length of the pendulum and g is the acceleration due to gravity.
• Since the mass and diameter are doubled, the acceleration due to gravity (g) on the planet will be half that of Earth.
• Therefore, the new period of oscillation will be √2 times the period on Earth, meaning if it was a second's pendulum on Earth, it will be 2√2 seconds on the planet.

Explanation

The potential energy (PE) of an object is calculated as:

PE = mass x gravity x height

= 1 kg x 10 m/s^2 x 1 m

= 10 Joule

So, the energy possessed by the body is 10 Joule.

Explanation

The gravitational force between two masses is mutual; each mass exerts an equal and opposite force on the other,.

It aligns with Newton's 3rd law of motion: for every action, there is an equal and opposite reaction.