Download Text 1 (1.1 What is physics?) Children have an insatiable curiosity

Text 1 (1.1 What is physics?)
Children have an insatiable curiosity about everything around them. Sights, sounds, and smells
are a constant source of wonder and amazement. They are eager to learn about nature by looking
at plants, birds, and insects, and by trying all sorts of experiments with straws, bottles, pebbles,
water, paint, balls, and of course food and mud. They also love to take apart a watch or a
mechanical toy to see what is inside and how it works. A scientist is a person who retains some
of this childlike sense of curiosity and wonder about nature.
Text 2 (4-4.1 Inertia and two-dimensional motion)
There appears to be a natural tendency of moving bodies to come to rest if left alone. For
example, a rolling ball eventually slows down and comes to a stop. Objects seem to require
external effort just to maintain their motion: A book moves along a table only as long as it is
pushed. It seems that the ‘natural’ state of bodies is to be at rest. But wait a moment. When the
brakes are applied on an icy road, a car continues to keep going. So what is the natural tendency
of bodies?
Text 3 (Particle dynamics I)
This chapter marks an important transition. We progress from the descriptions of kinematics
(how bodies move) to the explanations of dynamics (why bodies move). Dynamics is a branch of
mechanics in which the concept of force is used to account for the accelerated motion of bodies.
In everyday language, the term ‘force’ is used quite broadly. For example, the expressions ‘to
apply force’ and ‘to apply pressure’ are used interchangeably.
Text 4 (5.1 Force and mass)
In physics, we build on our intuitive understanding of force as either a push or a pull. Although
forces are not visible, we do see and experience their effects. Forces cause bodies to deform:
They expand springs, compress balloons, and bend beams. Also, as Newton’s first law implies, a
net (unbalanced) force will cause a body to change its velocity. These two effects are often seen
together. For example, a ball struck by a bat is both deformed and accelerated.
Text 5 (5.1 Force and mass)
Although every force is a manifestation of one of the fundamental interactions mentioned in
Section 1.1, it is sometimes convenient to refer to a force as being either a contact force or an
action at a distance. Contact forces arise when one body is in physical contact with another.
Examples include the forces exerted by ropes or springs, the forces involved in collisions, the
force of friction between two surfaces, and the force exerted by a fluid on its container.
Text 6 (5.4 Newton’s third law)
When you push against a wall, or pull at it, you experience a force in the opposite direction. The
harder you push (or pull), the harder the wall pushes (or pulls) back. In fact, the force exerted by
the wall on you is exactly equal in magnitude and opposite in direction to the force exerted by
you on the wall. This is an example of Newton’s third law, the law of action and reaction.
Text 7 (19 First law of thermodynamics)
When two bodies at different temperatures are placed in thermal contact, they ultimately reach a
common temperature somewhere between the two initial temperatures. We say that heat has
flowed from the hotter to the colder body. Heat, like light and force, impinges directly on our
senses, so everyone has an intuitive understanding of the term. Yet there is a subtlety in its
meaning that took many decades to clarify. Until the middle of the eighteenth century, the terms
heat and temperature had essentially the same meaning.
Text 8 (21 Entropy and the second law of thermodynamics)
The first law of thermodynamics is a statement of the conservation of energy. It allows any
process that conserves energy to occur. Yet several processes consistent with the first law do not
occur in nature. For example, an ice cube put in water does not discharge heat to raise the
temperature of the water. Heat always flows from a hot body to a cold body, never in the reverse
direction. When a body is dropped to the ground, its initial potential energy is converted to
kinetic energy and then, on impact, to internal energy of the body and its surroundings.
Text 9 (21.9 The availability of energy)
According to the first law, all forms of energy have equal status. Electrical, gravitational,
chemical, nuclear, and other forms of energy may, in principal, be fully converted from one form
to another. The second law addresses a lack of such symmetry when dealing with heat. Although
one can convert work completely into heat, it is a matter of experience that one cannot
completely convert heat into work – at least not in a continuous cycle.