Astronomy exam 2
5.4-3D The gravitational attraction of the Earth for other objects,
is smaller for objects farther from the Earth but never vanishes entirely.
5.3-2A The Law of Inertia states that a moving object will
keep moving if no force acts on it.
7.2-3B As viewed from the star Polaris, Venus
rotates clockwise and goes around the Sun counter-clockwise.
5.3.3H What total force will cause an object with a mass of 50kg to gain 1 meter per second every second?
50 Newtons.
5.3-6L A solar sail is a large sheet of light-reflecting plastic spread on an extremely low-mass framework and attached to a spacecraft. Sunlight exerts a force on the sail and moves the spacecraft. Suppose the spacecraft has a total mass of 5000kg (including the sail) and sunlight exerts a total force of 5N on the sail. What will be the acceleration of the spacecraft?
0.001m/s².
5.3-6I An ion rocket engine produces 50 Newtons of thrust. What acceleration can it give to a space probe with a mass of 10,000kg?
0.005 m/s².
6.1-1B The average radius of the Earth's orbit is
1.0 au.
5.3-5I Suppose that you try to lift an object by exerting an upward force of 5 Newtons on it. If gravity exerts a force of 20 Newtons downward on the object, what is the total force on the object?
15 Newtons downward.
6.1-3B If the planets are numbered from 1 to 8, going outward from the Sun, the planet Mars is number
4
5.3-5G Suppose that you try to lift an object by exerting an upward force of 5 Newtons on it. If gravity exerts a force of 10 Newtons downward on the object, what is the total force on the object?
5 Newtons downward.
5.3-3A What total force will cause an object with a mass of 1kg to gain 5 meters per second every second?
5 Newtons.
6.2-1D The density of water is 1000kg/m³, the density of rock is about 3000kg/m³, and the density of iron is 7800kg/m³. Which of the following densities is closest to the average density of the Earth?
5200kg/m³
6.4-1D Which of the following types of objects include things that could reasonably be described as "flying rocks" or, for the larger ones, "flying mountains?"
Asteroids.
6.5-2C Which of the following objects would be most likely to have a long elliptical orbit that takes it from far outside the orbit of Mars to a close approach to the Sun?
COMET
5.2-6B Galileo predicted that dropping a wooden ball and an iron ball at exactly the same time would result in them hitting the ground at the same time, so long as air friction was negligible. When he actually did the experiment, the balls hit the ground very close together, but sometimes the wooden ball hit first and sometimes the iron one hit first. If we repeat his experiment today, we find exactly the same thing. Which of the following conclusions is appropriate?
Galileo really did the experiment.
5.2-6D Galileo predicted that dropping a wooden ball and an iron ball at exactly the same time would result in them hitting the ground at the same time, so long as air friction was negligible. When he actually did the experiment, the balls hit the ground very close together, but sometimes the wooden ball hit first and sometimes the iron one hit first. If we repeat his experiment today, we find exactly the same thing. Which of the following conclusions is appropriate?
Galileo's theory was not disproven because the slight differences can be explained by defects in the experiment.
5.4-9C The International Space Station (ISS) is in a roughly circular orbit near the surface of the Earth, moving at around 5 miles per second. Suppose that it is desired to raise it to a new circular orbit, farther from the surface by having a rocket give it one or more short boosts. Which of the following schemes will work?
Increase its speed to 6 miles per second to put it on a rising path and give it another speed boost when its distance from the Earth stops increasing.
6.1-3A Which of these planets is the farthest from the Sun?
Mars
7.1-1C Which of the following planets can be said to have almost no atmosphere?
Mercury
6.2-2D It is expected that a normal terrestrial planet, with no accidental encounters that could add or subtract moons, should have
NO MOON
7.2-6A The first space probes to land on another planet were from the
Russian Venera series.
6.2-2B It is currently thought that moons typically do not form near
Terrestrial planets such as Earth and Mars.
6.7-1A Why couldn't we just fly a Space Shuttle to the Moon for at least a fly-by?
The Space Shuttle did not have enough fuel to reach escape velocity.
6.7-2A Why don't we just shoot all of our really nasty waste products into the Sun where they could not possibly bother anyone?
The Sun is actually the hardest part of the Solar System to get to from here.
5.3-7A A book, weighing 10 Newtons, sits on a table. Which of the following pairs of forces is an action-reaction pair?
The force that the book exerts on the table and the force that the table exerts on the book.
5.3-7B You are standing in an elevator that is accelerating upward at 1m/s². Which of the following pairs of forces is an action-reaction pair that have to be exactly equal and opposite to each other?
The force that the floor of the elevator exerts on you and the force that you exert on the floor of the elevator.
7.2-2D Water ice can be found on all but one of these planets. Which one has no ice?
VENUS
7.2-4C Which of the following planets has no magnetic field of any kind?
VENUS
5.1-2 The ancient greeks thought that
a heavy object should fall faster than a lighter object because the heavy object is pulled down with more force.
5.4-8A In comparison to Kepler's Laws of Planetary Motion, Newton's theory of Universal Gravitation predicted
almost the same motions but with corrections.
7.1-7C Space probes often use gravitational slingshot maneuvers. The main purpose of these maneuvers is to
change the direction and speed of the probe without using rockets.
5.4-9B Suppose that a spacecraft is in a roughly circular orbit near the surface of the Earth, moving at around 5 miles per second. Suppose the spacecraft flips over backwards and fires its rocket engine to slow its speed to 4.96 miles per second. The spacecraft will then
follow an ellipse that descends a bit and then rises again.
5.4-6A Freely falling objects with different masses fall with the same acceleration because
gravity exerts more force on the more massive object.
7.1-3A Mercury rotates so that it
has a solar day that last for two complete orbits around the Sun.
5.3-2D When the rocket engine in a spaceship stops firing, the spaceship keeps moving because
no force stops it.
5.4-8D When Newton's Laws were applied to predict the exact motion of the planet Uranus, the prediction failed to agree with very precise measurements. This failure led to the discovery
of the Planet Neptune.
7.1-5A The current model for the way that planets acquire magnetic fields requires which of the following combinations of things?
rotation and a core that contains a liquid electrical conductor.
5.4-2C When Newton calculated the magnitude of the acceleration of Earth's Moon relative to the Earth, and compared it to the acceleration of falling objects on the surface of the Earth, he found that
the Moon's acceleration was smaller.
6.1-1D An astronomical unit is defined to be
the average distance from the Earth to the Sun.
5.2-3 For an object that is moving along a straight path, the acceleration is
the change in the object's speed divided by the time it takes.
5.3-4D If you are told that an object that weighs 20 Newtons is raised a distance of 10 meters, you know that.
the force of gravity on the object is 20 Newtons.
5.1-2 Suppose that you drop two objects from the same height at the same time. Both objects are heavy enough to be unaffected by air resistance. If one object is twice as heavy as the other, Aristotle would predict that
the heavier object would hit the ground long before the lighter one.
5.5-4B If you are told that a 20 kilogram object is raised by 10 meters, you know that
the mass of the object is 20 kilograms.
5.4-3B In Newton's theory of gravity, everything is attracted
to every other object in the universe.
5.4-1B A planet that is following Kepler's Laws, accelerates
toward the Sun.
7.1-3D Mercury rotates so that its sidereal day lasts for
two thirds of a complete orbit around the Sun.
5.2-4 The Law of Inertia says that if an object is not acted on by any outside force, its acceleration
will always be zero
