Chapter Review:
After several centuries of careful observations, scientists have discovered that the behavior of
objects, both enormous and small, in the universe can be described and predicted by a series of
rules or principles often referred to as laws.; These laws describe the motion or velocity of
objects based on the amount of material or mass, an object contains and the force required to
move that mass. Using these laws, scientists have described such concepts as gravity, weight,
and momentum. These laws also make it possible for scientists to predict trajectories of the
space shuttle and the placement of Earth satellites used to transmit telephone conversations
and television programs as they orbit the Earth.
Chapter Objectives:
You should be able to do the following:
 Describe how the monument of Stonehenge was used by its builders to mark the
passage of the year.
 Relate how the process of scientific investigation studies in Chapter 1 was important in
the discovery and relationship between the disease cholera and human waste.
 Compare the models of planetary motion proposed by the early astronomers Ptolemy
and Copernicus.
 Describe how Johannes Kepler used the earlier observations of Tycho Brahe to more
accurately describe the planetary orbits.
 Discuss the historical importance of the scientists Galileo and his use of technology to
advance scientific knowledge.
 Differentiate between m=ass and weight.
 Distinguish between unifo4rm velocity and acceleration, and calculate these values for
an object relative to its mass.
 Define the gravitational force and show how it is related to the mass of two bodies and
the distance between them;
 Calculate what you would weight on the surface of the moon
Key Chapter Concepts
 In the ordinary world, we expect to discover natural causes for observed events.
 Predictability is the central principle of science.
 Observations over time allow us to make predictions about the positions of stars and
planets during the seasonal changes in the night sky.
 Stonehenge, a large circular monument of stones built more than 4000 years ago served
as a giant astronomical calendar used to mark the passage of the seasons.

 Scientists tend to accept the simplest explanation for a phenomenon as the most likely
explanation.
 Ancient scholars believed that the universe was perfect and that all movements of stars
and planets were based on spherical models.
 Spherical models did not explain the retrograde (apparent backward) motion of some
planets.
 Subsequent study revealed that the planetary orbits were actually elliptical, and not
spherical.
 Proper analysis and interpretation of observations in the universe depend on the
development of precise instruments and the application of mathematical techniques.
 Mechanics is the branch of science that deals with the motions of objects.
 Gravity is the attractive force between any two bodies in the universe.
o The law of universal acceleration was originally proposed by Isaac Newton and
has been overwhelmingly confirmed by scientific observations.
o Excessive acceleration, such as those experienced by astronauts and jet pilots,
may cause severe psychological effects.
 Three universal laws of motion (sometimes called Newton’s Laws) act in the universe:
o The First Law states that an object at rest will remain at rest or a moving object
will continue moving in a straight line, until acted on by an unbalanced force.
The tendency for an object to remain at rest or in uniform motion is called
inertia.
o The Second Law states that the acceleration produced on a body by a force is
proportional to the magnitude of the force and inversely proportional to the
mass of the object.
 The Second Law tells us that the harder you throw a ball, the faster (and
therefore, farther) it goes; and the more massive the ball, the shorter the
distance it can be thrown.
o The Third Law states that for every action, there is an equal and opposite
reaction.
 When one object, a baseball bat for example, pushes on another, such as
a baseball the ball also pushes against the bat, altering its motion.
 Forces always act simultaneously in pairs.
 Every motion in life, from the swimming of a fish to the flight of a rocket
ship, involves the interplay of all three of Newton’s laws.
 Weight is the measure of the force of gravity on an object stays, the same no matter
where the object is located.
 Mass, the amount of matter present in an object, stays the same no matter where the
object is located.
 Even though the universal laws of motion explain all movement in the universe, the
uncertainty of actual events precludes our ability to accurately predict events with
absolute certainty.