Deck 3: Orbits and Gravity

Question 1

Why do many people consider Isaac Newton one of the greatest scientists who ever lived?

A) He formulated the laws that govern all motion in the universe
B) He combined the work of Galileo, Brahe, and Kepler into one framework
C) He figured out the mathematical form of a law of universal gravity
D) all of the above
E) none of the above (not a, not b, not c)

Answer 1

all of the above

Question 2

In an ellipse, the ratio of the distance between the foci and the length of the major axis is called:

A) the eccentricity
B) the semi-major axis
C) perihelion
D) the astronomical unit
E) Newton's ratio

Answer 2

the eccentricity

Question 3

When NASA and a group of astronomers sent up a spacecraft designed to find planets orbiting other stars, they named it after Kepler. Why was this an appropriate name?

A) Kepler used his telescope to find the first planet orbiting another star
B) Kepler was the first person to express the law of universal gravity in mathematical terms
C) Kepler figured out the rules of planetary motion, which planets in our solar system and planets elsewhere must obey
D) Kepler was the first person to suggest how to launch rockets into space
E) Kepler designed the first telescope ever built
3)2 Newton's Great Synthesis

Answer 3

Kepler figured out the rules of planetary motion, which planets in our solar system and planets elsewhere must obey

Question 4

When a planet, in its orbit, is closer to the Sun, it:

A) moves slower than average
B) reflects less sunlight than average
C) feels less gravitational pull than average
D) moves faster than average
E) spins faster on its axis

Question 5

The idea that objects (in the absence of an outside force) tend to continue doing what they are already doing is called the law of

A) eccentricity
B) inertia
C) action-reaction
D) angular momentum
E) Congressional action

Question 6

To come up with the precise mathematical form of his law of gravity, Newton first had to invent the mathematical techniques that we now call:

A) algebra
B) ratio and proportions
C) angular momentum
D) calculus
E) scientific notation

Question 7

According to Kepler's third law, there is a relationship between the time a planet takes to revolve around the Sun and its

A) size
B) period of rotation
C) distance from the Sun
D) eccentricity
E) astrological sign

Question 8

Which of the following has the greatest density?

A) a cubic meter of snow
B) a cubic meter of air
C) a cubic meter of astronomy textbooks (the printed versions, not the on-line ones)
D) a cubic meter of feathers
E) a cubic meter of lead

Question 9

After a long night of cramming for a test, your college room-mate hits his head forcefully against the wall of your room in despair. According to Newton's 3^rd Law, as he exerts a force against the wall, there must be an equal and opposite force. How does that opposite force show itself in this case?

A) Your room-mate is pulled downward by gravity
B) The wall exerts a force on your room-mate's head and he has a headache
C) The wall has a huge dent in it
D) There is an exception to the Law for solid objects like walls, so there is no opposite force
E) The resident assistant assigned to your floor makes a complaint against the two of you
3)3 Newton's Universal Law of Gravitation

Question 10

Why do astronauts (and cans of soft drink) float around in the Shuttle instead of falling?

A) the Shuttle is so far from the Earth, gravity is negligible
B) the Shuttle's gravity balances the Earth's, so that the net gravity is zero
C) the Shuttle is falling around the Earth (and everything aboard is in free fall)
D) the Shuttle has an antigravity device on board, developed by NASA
E) the rules Newton developed for gravity only hold on Earth, not once you get into space

Question 11

What specific event really made it possible for the three laws of planetary motion to be discovered?

A) a brilliant comet in 1601 blazed across the sky and was seen to cross in front of Venus
B) Tycho Brahe died and his assistant was able to get full access to his data
C) Galileo's books were published in Danish and became widely available to the public
D) an alignment of all the known planets in one part of the sky called everyone's attention to them
E) the plague broke out in England and forced Isaac Newton to return home from college

Question 12

Newton showed that to change the direction in which an object is moving, one needs to apply:

A) a force
B) an orbit
C) an inertia
D) a perigee
E) a bribe

Question 13

Astronomers discover a new comet that orbits the Sun, but has its aphelion (the furthest point in its orbit) beyond Neptune. Astronomers studying this comet have the right to expect that it:

A) will follow Newton's laws of motion
B) will move ahead in a straight line at a steady speed because of the law of inertia
C) will not obey Newton's universal law of gravitation
D) will not have an equal and opposite force in empty space when the force of the Sun's gravity pulls on it
E) astronomer have no right to expect ANY of the above.

Question 14

An astronomy textbook, when printed out, weighs four pounds on the surface of the Earth. After finishing your course, you are so tired of the book, you arrange for NASA to shoot it into space. When it is twice as far from the center of the Earth than when you were reading it, what would it weigh? (Note, assume that the book has been moving away from the Earth, not falling freely around it.)

A) 4 lbs
B) 8 lbs
C) 2 lbs
D) 1 lb
E) 16 lbs

Question 15

Which of the following statements about the force of gravity is FALSE?

A) it is a universal force, which acts everywhere in space
B) its strength decreases as the square of the distance
C) its strength is inversely proportional to the mass: the more mass, the less gravity
D) the force never becomes zero
E) it causes the paths of the planets to be ellipses and not straight lines

Question 16

Which of the following statements about forces is FALSE?

A) forces change the momentum of a body
B) forces cause an acceleration to take place
C) forces always occur in equal and opposite pairs
D) where there is no force, objects continue to move the way they were moving
E) there are places on Earth where all forces are absent

Question 17

In Newton's Law of Gravity, the force of gravity goes up as the:

A) mass goes down
B) distance goes up
C) mass goes up
D) distance goes down
E) more than one of the above

Question 18

The 17th century astronomer who kept a roughly 20 year continuous record of the positions of the Sun, Moon, and planets was:

A) Tycho Brahe
B) Galileo Galilei
C) Isaac Newton
D) Nicolaus Copernicus
E) Jean Luc Picard

Question 19

A single star in the process of forming starts by spinning slowly (while it is quite large and relatively cool.) As the star collapses under the pull of its own gravity, its size decreases. As a result, its rate of spinning:

A) will increase
B) will decrease
C) will stay the same
D) will either increase or decrease depending on the star's temperature
E) this question cannot be answered from the information we are given

Question 20

We now know that the orbit of a stable planet around a star like the Sun is always in the shape of:

A) a circle
B) a parabola
C) a straight line
D) an ellipse
E) none of the above

Question 21

Newton's reformulation of Kepler's third law allows us to measure the masses of bodies in orbit around each other, if we can measure:

A) the rotation rate of each object
B) the distances and periods of revolution
C) the eccentricities and semi-major axes
D) the force and the reaction force
E) the sweetness of those fig-filled cookie bars

Question 22

The asteroid belt is

A) a region of icy chunks of material beyond the orbit of Pluto
B) a zone where rocky chunks orbit between Mars and Jupiter
C) a series of orbital zones around the Moon, from which fragments drop down to form craters
D) is a region around the Earth from which meteors (shooting stars) are observed to drop
E) a new fashion accessory being sold by NASA to raise funds for future missions
3)5 Motions of Satellites and Spacecraft

Question 23

The first artificial satellite the human race lofted into orbit was called:

A) Pioneer
B) Explorer
C) Newton
D) Sputnik
E) Luna

Question 24

The minimum speed required to launch an object so that it remains the same distance above the ground and just falls around the Earth is called:

A) perigee speed
B) circular satellite velocity
C) Newtonian orbit velocity
D) the Keplerian speed
E) the speed of sound (or Mach 1)

Question 25

To figure out what you weigh on the surface of the Moon (how much gravity there pulls you downward), you need to know

A) just the mass of the Moon
B) just the distance from the Moon's center to its surface
C) just the size of the Moon's orbit around the Earth (its semi-major axis, say)
D) which part of its orbit the Moon is in
E) two of the above factors
3)4 Orbits in the Solar System

Question 26

Small changes in the orbits of planets caused by the gravitational pull of the other planets in the solar system are called:

A) perturbations
B) reaction forces
C) foci
D) perigee pulls
E) eccentricities

Question 27

The planet in our solar system whose orbit actually brings it inside the orbit of another planet is:

A) Neptune
B) Pluto
C) Earth
D) Mars
E) Mercury

Question 28

Why do satellites launched into low-Earth orbits not remain there indefinitely?

A) they do not have enough speed to fall freely around the Earth
B) they tend to collide with other spacecraft and spacecraft fragments
C) they lose speed due to friction with the upper layers of the Earth's atmosphere
D) they run out of fuel, and without fuel, all satellites, no matter what their orbit is, must fall
E) this is an unsolved problem, but a NASA committee has been assigned to work on it

Question 29

To leave the gravitational pull of the Earth, and explore other planets, satellites must have at least:

A) circular satellite velocity
B) escape velocity
C) perigee velocity
D) three orbit perturbation
E) the permission of one Congressional committee

Question 30

When a comet like Comet Hale-Bopp comes closest to the Sun in its orbit, we say that it is at:

A) circular satellite velocity
B) the minimum angular momentum point
C) perihelion
D) apogee
E) the tail end of its journey

Question 31

Credit for the discovery of Neptune is shared by two astronomers. They are:

A) Hubble and Humason
B) Kepler and Newton
C) Adams and Leverrier
D) Doppler and Wien
E) Fraknoi and Morrison

Question 32

The planet in our solar system with the shortest period of revolution is:

A) Mercury
B) Pluto
C) Jupiter
D) Venus
E) you can't fool me, all the planets have the same period of revolution

Question 33

The Earth's escape speed (the speed you need to get away forever) is about 25,000 miles per hour. Escape speed depends on the gravity of the object trying to hold the spacecraft from escaping. Based on your understanding of gravity, how will the escape speed from the Moon compare to the escape speed from Earth?

A) The Moon's escape speed will be greater than Earth's
B) The Moon's escape speed will be smaller than Earth's
C) The Moon's escape speed will be exactly the same as Earth's
D) The Moon's escape speed will change depending on whether it's a crescent Moon or a full Moon
E) The Moon's escape speed will be balanced by the Earth being so close and it will be zero
3)6 Gravity with More Than Two Bodies

Question 34

According to Kepler's 2nd Law, comets (which have eccentric orbits) should spend a lot more of their time:

A) close to the planets
B) close to the Sun
C) losing angular momentum
D) far from the Sun
E) increasing the rate at which they spin

Question 35

The planet Neptune was discovered by means of:

A) careful observations of its motion by one astronomer in England (done over most of his lifetime)
B) observations of its motion performed over many years by astronomers all over the globe
C) radio observations of its large magnetic field
D) mathematical calculations of how it was perturbing the motion of a neighbor planet
E) discrepancies in the horoscopes of famous actors and actresses; errors in the horoscopes showed astrologers that there must be another cosmic influence on their love lives