Question 1

Consider an object on a circular orbit around the Sun.Which of the following quantities remains unchanged throughout the orbit?

Accepted Answer

According to Kepler's Second Law, a planet moves faster when it is closer to the Sun and slower when it is farther away. However, the object still maintains a constant speed around the orbit, meaning that choice B (speed) remains unchanged while the other options may change depending on the position of the object along the orbit.

Question 2

Galileo overturned Aristotelian physics by showing that:

Accepted Answer

Galileo's experiments demonstrated that objects accelerate as they fall, challenging the Aristotelian view that heavier objects fall faster than lighter ones.

Question 3

Galileo was put on trial by the Catholic Church for:

Accepted Answer

Galileo was put on trial by the Catholic Church primarily for publishing "Dialogue Concerning the Two Chief World Systems" in 1632, which defended the heliocentric model of the universe, challenging the Church's geocentric view.

Question 4

A rocket engine accelerates its exhaust gas in one direction,moving the rocket in the other direction.Which law explains this phenomenon?

Accepted Answer

Newton's third law states that for every action, there is an equal and opposite reaction. In this case, the action is the expulsion of exhaust gases out of the rocket engine in one direction, and the reaction is the movement of the rocket in the opposite direction.

Question 5

Which of the following people was the first to introduce experimental methods to science?

Accepted Answer

Although Aristotle and other ancient philosophers developed theories about the natural world, they relied on observation and deduction rather than experimentation. Nicolaus Copernicus used mathematics to develop his heliocentric model of the universe, but did not conduct experiments. Isaac Newton built upon experimental methods, but he came after Galileo. Galileo Galilei was the first to introduce experimental methods to science, conducting experiments to test his theories about motion and the behavior of objects in freefall, among other things.

Question 6

A ball is launched upward from a baseball field.Assuming that it begins with an upward velocity of 10.5 m/s,what is its speed after three seconds have elapsed? (The acceleration due to gravity on Earth is 9.8 m/s².)

Accepted Answer

Using the formula

v = u + at

where

v = final velocity 
u = initial velocity = 10.5 m/s (given)
a = acceleration due to gravity = -9.8 m/s² (negative because it opposes the upward motion)
t = time = 3 s (given)

Substituting the values, we get

v = 10.5 - 9.8(3) 
v = 10.5 - 29.4 
v = -18.9 m/s

Note that the negative sign indicates that the velocity is downward. However, the problem asks for the speed, which is the magnitude of the velocity. Therefore, we take the absolute value, giving

speed = |-18.9| 
speed = 18.9 m/s

Thus, the ball's speed after three seconds is 18.9 m/s, which corresponds to choice C.

Question 7

An asteroid follows a circular orbit around the Sun with a radius of 5 AU.Which of the following is closest to its orbital period?

Accepted Answer

Using Kepler's Third Law, which states that the square of the orbital period (T) of a planet is directly proportional to the cube of the semi-major axis (a) of its orbit, $T^2 \propto a^3$. Given that the Earth's orbit is 1 AU and it takes 1 year to orbit the Sun, for an asteroid at 5 AU, its orbital period can be calculated as $T^2 = (5)^3 = 125$, so $T = \sqrt{125} \approx 11$ years.

Question 8

Two asteroids,A and B,orbit the Sun on circular orbits with radii of 1 AU and 4 AU,respectively.How do their orbital velocities compare to each other?

Accepted Answer

The orbital velocity of an object around the Sun is inversely proportional to the square root of the radius of its orbit. Therefore, if asteroid A is 1 AU from the Sun and asteroid B is 4 AU from the Sun, asteroid A's orbital velocity will be twice that of asteroid B, because the square root of 4 is 2.

Question 9

An object travels at 10 m/s through interstellar space.If no forces act upon it,it will:

Accepted Answer

The object will continue with the same velocity, as there are no forces acting upon it to cause it to accelerate, slow down, or change direction. In the absence of any force, an object will continue in a straight line with a constant velocity.

Question 10

According to Newton,satellites orbit Earth because:

Accepted Answer

Satellites orbit Earth because of gravitational forces between the two bodies. Newton's law of gravitation states that every object in the universe attracts every other object with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This force keeps the satellite in orbit around Earth. The other options (B, C, and D) are related to the motion of objects but do not fully explain why satellites orbit Earth.

Question 11

Which of the following observations provided the most direct challenge to the geocentric model of solar system orbits?

Accepted Answer

The phases of Venus directly challenged the geocentric model because they showed that Venus was circling the Sun, not the Earth. As Venus orbited the Sun, we observed it going through phases just like the Moon does. This was only possible if Venus was on a different orbit than Earth, which contradicts the geocentric model where all planets orbit the Earth. The other observations listed are not direct challenges to the geocentric model.

Question 12

Which of the following correctly characterizes the velocity and angular momentum of a planet orbiting the Sun?

Accepted Answer

According to Kepler's laws, the planet's velocity is maximum at perihelion (closest point to the Sun) and minimum at aphelion (farthest point from the Sun). However, the angular momentum is constant throughout the orbit, as there is no external torque acting on the system. Therefore, the correct choice is D, which states that the velocity is maximum at perihelion, while the angular momentum is constant throughout the orbit.

Question 13

A physicist launches two asteroids in circular orbits with identical angular momenta.Asteroid A's orbit has twice the radius of Asteroid B's orbit.How do their orbital velocities compare to each other?

Accepted Answer

According to Kepler's second law, the orbital velocity of a planet is inversely proportional to its distance from the Sun. In other words, the closer a planet is to the Sun, the faster it moves, and the farther away it is, the slower it moves. Since Asteroid A's orbit has a larger radius than Asteroid B's orbit, it must move slower than Asteroid B to conserve angular momentum. Therefore, the correct answer is B, Asteroid A moves slower than Asteroid B.

Question 14

Who was the first astronomer to make measurements of the sky with a telescope?

Accepted Answer

Galileo Galilei is credited with being the first astronomer to make detailed observations of the sky using a telescope. He made numerous discoveries, including the four largest moons of Jupiter and the phases of Venus, which provided evidence for the heliocentric model of the solar system. While Copernicus and Brahe made important contributions to astronomy before him, they did not use telescopes in their work. Likewise, Newton made important contributions to physics and mathematics, but was not primarily an astronomer.

Question 15

Which of the following observations provided the most direct challenge to the Aristotelian view of the nature of celestial objects?

Accepted Answer

The Aristotelian view held that celestial objects were perfect and unchanging. The observation of the Moon's topography, with its mountains and craters, directly challenged this view by showing that celestial bodies were not perfect spheres.

Question 16

Two asteroids,A and B,orbit the Sun.Asteroid A follows a circular orbit with a radius of 6 AU.
Asteroid B follows an elliptical orbit with a perihelion distance of 4 AU and an aphelion distance of 8 AU.
How do their orbital periods compare to each other?

Accepted Answer

According to Kepler's third law of planetary motion, the square of the orbital period of a planet (or asteroid, in this case) is directly proportional to the cube of the semi-major axis of its orbit. For asteroid A, the radius of its circular orbit is 6 AU, which is also its semi-major axis. For asteroid B, the semi-major axis of its elliptical orbit is the average of its perihelion and aphelion distances, which is (4 AU + 8 AU) / 2 = 6 AU. Since both asteroids have the same semi-major axis length, their orbital periods are identical, regardless of the shape of their orbits.

Question 17

Two asteroids have elliptical orbits around the Sun with the same semimajor axes but different eccentricities.Which of the following statements is true?

Accepted Answer

The eccentricity of an orbit determines its shape, with higher eccentricity indicating a more elongated ellipse. An orbit with a larger eccentricity will have a larger variation in distance from the Sun throughout its orbit, leading to a larger change in speed due to Kepler's second law, which states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This means that the speed of the asteroid increases as it gets closer to the Sun and decreases as it moves away, with the change in speed being more pronounced for orbits with higher eccentricity.

Question 18

Pluto is about 40 times farther from the Sun than Earth is.How much smaller is Pluto's acceleration due to the Sun's gravity than Earth's?

Accepted Answer

The acceleration due to gravity is inversely proportional to the square of the distance between two objects. Therefore, the acceleration due to the Sun's gravity on Pluto is (1/40)^2 = 1/1600 times the acceleration due to the Sun's gravity on Earth. The format of the answer should include the fraction in numerical form with the scientific notation.

Question 19

Who was the first astronomer to discover sunspots?

Accepted Answer

Galileo Galilei was the first astronomer to discover sunspots in 1610 through his telescope.

Question 20

Two balls are dropped from rest in a vacuum chamber on Earth.They have identical sizes,but the red ball is twice as massive as the blue ball.What happens?

Accepted Answer

According to the law of gravitation, the gravitational force acting between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. In a vacuum, both balls experience the same gravitational force from Earth since they are dropped from the same height. As the size or shape of the object does not affect the acceleration due to gravity, both balls will accelerate at the same rate towards the Earth, irrespective of their masses. Therefore, the best choice is A) The balls accelerate at the same rate.

Quiz 3: A Universe of Universal Laws