Universal Law of Gravitation MCQ Quiz - Objective Question with Answer for Universal Law of Gravitation - Download Free PDF

CONCEPT:

Weightlessness in Space

• Weightlessness occurs when there is no net force acting on a body, making it appear as though it has no weight.
• In the context of an astronaut on the International Space Station (ISS), this sensation is due to the fact that both the astronaut and the ISS are in free-fall around the Earth.

EXPLANATION:

• An astronaut experiences weightlessness because:
  • The normal reaction of the space-station floor on the astronaut is zero.
  • The astronaut and the space station are both accelerating towards the Earth at the same rate due to gravity, creating a continuous free-fall scenario.
• However, it does not mean that:
  • The gravitational pull of Earth on the astronaut is zero. The gravitational force is still acting on the astronaut, which is why they are in orbit.
  • The acceleration of the astronaut is zero. They are accelerating towards the Earth due to gravity, but this acceleration is what creates the orbit.
  • The space station applies a centrifugal force on the astronaut. The sensation of weightlessness is due to the free-fall, not a centrifugal force.

Therefore, the correct statement is that the normal reaction of the space-station floor on the astronaut is zero.

CONCEPT:

Weightlessness in Space

• Weightlessness occurs when there is no net force acting on a body, making it appear as though it has no weight.
• In the context of an astronaut on the International Space Station (ISS), this sensation is due to the fact that both the astronaut and the ISS are in free-fall around the Earth.

EXPLANATION:

• An astronaut experiences weightlessness because:
  • The normal reaction of the space-station floor on the astronaut is zero.
  • The astronaut and the space station are both accelerating towards the Earth at the same rate due to gravity, creating a continuous free-fall scenario.
• However, it does not mean that:
  • The gravitational pull of Earth on the astronaut is zero. The gravitational force is still acting on the astronaut, which is why they are in orbit.
  • The acceleration of the astronaut is zero. They are accelerating towards the Earth due to gravity, but this acceleration is what creates the orbit.
  • The space station applies a centrifugal force on the astronaut. The sensation of weightlessness is due to the free-fall, not a centrifugal force.

Therefore, the correct statement is that the normal reaction of the space-station floor on the astronaut is zero.

CONCEPT:

Weightlessness in Space

• Weightlessness occurs when there is no net force acting on a body, making it appear as though it has no weight.
• In the context of an astronaut on the International Space Station (ISS), this sensation is due to the fact that both the astronaut and the ISS are in free-fall around the Earth.

EXPLANATION:

• An astronaut experiences weightlessness because:
  • The normal reaction of the space-station floor on the astronaut is zero.
  • The astronaut and the space station are both accelerating towards the Earth at the same rate due to gravity, creating a continuous free-fall scenario.
• However, it does not mean that:
  • The gravitational pull of Earth on the astronaut is zero. The gravitational force is still acting on the astronaut, which is why they are in orbit.
  • The acceleration of the astronaut is zero. They are accelerating towards the Earth due to gravity, but this acceleration is what creates the orbit.
  • The space station applies a centrifugal force on the astronaut. The sensation of weightlessness is due to the free-fall, not a centrifugal force.

Therefore, the correct statement is that the normal reaction of the space-station floor on the astronaut is zero.

CONCEPT:

Geostationary Satellite

• A geostationary satellite is a type of satellite that appears to be stationary with respect to a fixed point on Earth.
• It orbits the Earth at the same rotational speed as the Earth, allowing it to stay fixed above a specific longitude.
• To achieve this, the satellite must be placed in a circular orbit directly above the Earth's equator.
• The height of a geostationary satellite is determined by the balance between the gravitational force and the centripetal force required for its circular motion.

EXPLANATION:

• The height of a geostationary satellite is approximately 36,000 kilometers above the Earth's surface.
• This specific height is derived based on the condition that the satellite's orbital period matches the Earth's rotational period, which is 24 hours.
• At this altitude:
  • The gravitational force provides the necessary centripetal force for the satellite's circular motion.
  • The satellite appears stationary relative to an observer on Earth because its orbital angular velocity matches Earth's rotational angular velocity.

Therefore, the geostationary satellite is placed at a height of about 36,000 km above the Earth's surface.