Question 1

How was the planet Neptune discovered?

Accepted Answer

Neptune was discovered by mathematical prediction using Newton's laws. In the mid-19th century, astronomers observed Uranus deviating from its expected orbit. French mathematician Urbain Le Verrier used these observations to predict the existence and location of another planet beyond Uranus. Johann Galle and Heinrich d'Arrest observed Neptune for the first time on September 23, 1846, within 1° of the position Le Verrier had predicted.

Question 2

In the years after Newton published his laws of motion,it was found that the observed positions of the planet Uranus did not match the predictions of Newton's theory.The reason for this turned out to be:

Accepted Answer

The observed positions of Uranus could only be explained by the gravitational influence of a previously unknown planet, which was later discovered and named Neptune. This discovery confirmed the validity of Newton's laws of motion and gravity, and no discrepancies were found until the advent of Einstein's general relativity theory, which provided a more accurate description of gravity in extreme conditions.

Question 3

The International Space Station is in orbit around Earth.If an astronaut aboard the station releases an object in mid-air,it will:

Accepted Answer

Objects in the International Space Station are in a state of freefall, which means they are continuously falling towards the Earth but their horizontal motion allows them to stay in orbit around the Earth. If an astronaut releases an object in mid-air, it will continue to follow the same motion as the Space Station and also fall towards the Earth due to the gravitational force. Therefore, the correct choice is B.

Question 4

Who predicted the existence of the planet Neptune before it was discovered observationally?

Accepted Answer

Neptune was predicted to exist mathematically by John Couch Adams and Urbain Le Verrier in 1846, based on irregularities in the orbit of Uranus.

Question 5

A person orbiting Earth in the space shuttle feels weightless because:

Accepted Answer

In orbit, the person and the space shuttle are both accelerating towards the center of the Earth due to gravity. Therefore, there is only one force acting on the person (gravity), but since the shuttle and the person are accelerating together, the shuttle does not push up on the person, creating the feeling of weight. This gives the person the sensation of weightlessness.

Question 6

How much gravitational force acts on an astronaut in the space shuttle in a circular orbit 300 km above Earth's surface?

Accepted Answer

The gravitational force decreases with distance from the Earth's center, but at 300 km above the surface, it is still significant, though slightly less than on the surface.

Question 7

Which object was discovered after its position had been predicted by the application of Newtonian mechanics to the deviation in the motion of another planet?

Accepted Answer

Neptune was discovered after its position was predicted based on the deviation in Uranus's motion. This led astronomers to conclude that another planet must be influencing Uranus's orbit. The position of Neptune, based on these calculations, was then confirmed through observations.

Question 8

If two massive bodies,initially held at rest in space,are released,then they will begin to:

Accepted Answer

According to Newton's law of gravitation, any two masses in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. When two massive bodies, initially held at rest in space, are released, they start moving towards each other as they attract each other due to the force of gravity. Hence, the correct answer is B.

Question 9

Which object was discovered mathematically using Newton's laws before it was discovered observationally through the telescope?

Accepted Answer

Neptune was discovered mathematically by French mathematician Urbain Le Verrier using Newton's laws before it was observed through telescopes in 1846.

Question 10

An object is in an orbit caused by its gravitational attraction to the Sun.This orbit:

Accepted Answer

An object in orbit around the Sun can have different shapes for its path depending on its initial conditions. If the orbit has a fixed point (called the focus) such that the sum of the distances from the focus to any point on the path is constant, then the orbit is an ellipse. If the orbit is open and the object is moving fast enough to escape the Sun's gravity, then the path will be a hyperbola. If the object is moving at exactly the escape velocity, then its path will be a parabola. Therefore, an object in orbit around the Sun might be in an ellipse, a parabola, or a hyperbola.

Question 11

What happens to objects that acquire enough energy to transition to hyperbolic orbits within the solar system?

Accepted Answer

When an object acquires enough energy to transition to a hyperbolic orbit within the solar system, it means that it has achieved escape velocity and will not return. Therefore, it will make only a single pass near the Sun and then leave the solar system forever, as option A states.

Question 12

Suppose that an object is discovered moving around the Sun once every 120 years.Which of the following paths is a possible orbit for this object?

Accepted Answer

An object that orbits around the Sun once every 120 years must have a closed trajectory since it comes back to the same position in space after 120 years. A straight line or a parabolic orbit would not result in a closed trajectory. A hyperbolic orbit would imply that the object is moving away from the Sun forever, which cannot be the case if it orbits around the Sun periodically. Only an elliptical orbit would satisfy the condition of a periodic, closed trajectory around the Sun.

Question 13

Which objects are often found to follow hyperbolic orbits?

Accepted Answer

Comets are known to have hyperbolic orbits as they are often observed coming from the distant Oort cloud and on their way towards the inner solar system, they follow a hyperbolic trajectory. This is due to their high eccentricity and velocity. Other objects in the solar system typically follow elliptical or circular orbits, except in rare cases such as some artificial satellites or interstellar objects.

Question 14

The first person to derive the elliptical shape of planetary orbits from basic physics and mathematics (not from observations of planetary positions)was:

Accepted Answer

Isaac Newton was the first to derive the elliptical shape of planetary orbits from basic physics and mathematics, specifically through his laws of motion and universal gravitation.

Question 15

In the years after Newton published his laws of motion,it was found that the observed positions of the planet Uranus did not match the predictions of Newton's theory.The reason for this turned out to be the:

Accepted Answer

Uranus's observed positions did not match the predictions of Newton's theory due to the perturbing effect of Neptune, which had not yet been discovered at that time.

Question 16

Suppose two asteroids are located at the same distance from the Sun.One asteroid has twice the mass of the other.According to Newton's law of gravitation (and ignoring all forces except that from the Sun):

Accepted Answer

According to Newton's law of gravitation, the force between two objects is directly proportional to their masses and inversely proportional to the square of the distance between them. Since both asteroids are located at the same distance from the Sun, the only factor that affects the force is their mass. Therefore, the more massive asteroid feels twice the force that the other does, as the force is directly proportional to their masses.

Question 17

The first major astronomical prediction of Newton's theory of gravitation to be confirmed by observation was the:

Accepted Answer

The return of Halley's Comet in 1758 was predicted using Newton's theory of gravitation, and its appearance confirmed the accuracy of his predictions.

Question 18

Which of the following situations describes an acceptable path for a body gravitationally bound to the Sun?

Accepted Answer

According to Kepler's laws of motion, a body gravitationally bound to the Sun will follow an elliptical path with the Sun at one focus. Therefore, the only acceptable path among the given options is the long ellipse with the Sun at one focus (choice C). A parabolic path (choice A) implies that the body is not bound to the Sun and will leave the solar system. A circular path (choice B) implies that the body is not in a gravitationally bound orbit and will require a constant external force to maintain its motion, which is not the case for natural planets and other bodies. A long ellipse with the Sun at its center (choice D) violates Kepler's law that the Sun should be at one focus of the elliptical orbit.

Question 19

How was the planet Uranus discovered?

Accepted Answer

Uranus was discovered by William Herschel on March 13, 1781, while he was conducting a telescopic survey of the sky. He initially thought it was a comet, but further observations showed that it had a planetary orbit.

Question 20

Who was the discoverer of the planet Uranus?

Accepted Answer

William Herschel discovered Uranus in 1781. Galileo Galilei did not discover Uranus, but he did discover four of Jupiter's largest moons in 1610. Johann Galle discovered Neptune in 1846, not Uranus. Clyde Tombaugh discovered Pluto in 1930.

Quiz 2: Gravitation and the Waltz of the Planets