Download Physics Study Guide - The Oakwood School

Physics Study Guide
1. Review the following pages (textbook) + the Supplemental Problems you
received:
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Chapter 1: p. 23
Chapter 2: p. 51
Chapter 3: p. 79
Chapter 4: p. 111
Chapter 5: 139
Chapter 6: 163
Chapter 7: p. 189
2. Review the handout on Einstein and timeline for E=mc2 video.
3. Concept Summary
Science is the study of nature’s rules.
Science is a way of thinking as well as a body of knowledge.
 Physics is the most basic of all sciences.
 The use of mathematics helps make ideas in science unambiguous.
Scientific methods are procedures for answering questions about the world by
testing educated guesses (hypotheses) and formulating general rules.
 Hypotheses in science must ne testable. They are changed or abandoned if
they are contradicted by experimental evidence.
A scientific theory is a body of knowledge and well-tested hypotheses about
some aspect of the natural world.
 Theories are modified as new evidence is gathered.
Science deals with knowledge for its own sake, while technology is an
application of scientific knowledge.
 Science deals with theoretical questions, while technology deals with
practical problems.
Motion is described relative to something. Speed is a measure of how fast
something is moving.
 Speed is the rate as which distance is covered, and it is measured in units of
distance divided by time.
 Instantaneous speed is the speed at any instant.
 Average speed is the total distance covered divided by the time interval.
Velocity is speed together with direction.
 Velocity is constant only when speed and direction are both constant.
Acceleration is the rate at which velocity is changing with respect to time.
 An object accelerates when its speed is increasing, when its speed is
decreasing, and/or when its direction is changing.
 Acceleration is measured in units of speed divided by time.
An object in free fall is falling under the influence of gravity alone when air
resistance does not affect its motion.
 An object in free fall has a constant acceleration of 9.80 m/s2.
Vector quantities have both magnitude and direction. A vector is represented by
an arrow whose length represents the magnitude of the vector quantity and
whose direction represents the direction of the vector quantity.
The resultant of two velocities can be determined from a vector diagram drawn
to scale.
Any single vector can be replaced by two components that add by vector rules to
form the original vector.
When gravity is he only force acting in a projectile near Earth, the horizontal
component of its velocity does not change.
A satellite is continually falling around Earth
Galileo concluded that if it were not for friction, an object in motion would keep
moving forever.
Newton’s first law of motion-the law of inertia:
Every object continues in a state of rest, or in a state of motion in a straight line
at constant speed, unless it is compelled to change that state by forces exerted
upon it.
Inertia is the resistance an object has to a change in its state of motion.
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Mass is a measure of inertia.
Mass is not the same as volume.
Mass is not the same as weight.
The mass of an object depends only on the number and kind of atoms in it.
Mass does not depend on the location of the object.
The weight of an object is the gravitational force acting on it. Weight
depends on the location of the object.
The net force, which is the vector sum of all forces acting in an object, affects the
object’s state of motion.
 When an object is at rest, its weight is balanced by an equal and opposite
support force.
 An object is in equilibrium when it is at rest, with zero net force acting on it.
Newton’s second law of motion:
The acceleration produced by a net force on an object is directly proportional
to the magnitude of the net force, is in the same direction as the net force, and
is inversely proportional to the mass of the object.
a~F/m
An object accelerates – changes speed and/or direction – when a net force acts
on it.
 The acceleration of an object is directly proportional to the net force acting
on it.
 The acceleration of an object is inversely proportional to the mass of the
object.
 Acceleration equals net force divided by mass.
 Acceleration is in the same direction as the net force.
When an object moves with constant velocity while an applied force acts on it, an
equal and opposite force, usually friction, must also act to balance the applied
force.
The application of a force over an area produces pressure.
 When the force is perpendicular to the surface area, the pressure equals the
force divided by the area over which it acts.
The acceleration of all objects in free fall is the same, regardless of their mass.
 When air resistance is present, a falling object accelerates only until it
reaches its terminal speed.
 At terminal speed, the force of air resistance balances the force of gravity.
Newton’s third law of motion:
Whenever an object exerts a force on a second object, the second object exerts
an equal and opposite force on the first object.
An interaction between two things produces a pair of forces.
 Interacting things exert forces on each other.
 The two interacting forces are called the action force and the reaction force.
 Action and reaction forces are equal in strength and opposite in direction.
An object rotates when it turns around an internal axis; it revolves when it turns
around an external axis.
 Rotational speed is the number of rotations or revolutions made per unit of
time.
A centripetal force pulls objects toward a center.
 An object moving in a circle is acted on by a centripetal force.
 When an object moves in a circle, there is no force pushing the object
outward from the circle.
 From within a rotating frame of reference, there seems to be an outwardly
directed centrifugal force, which can simulate gravity.
The moon and other objects in orbit around Earth are actually falling toward
Earth but have great enough tangential velocity to avoid hitting Earth.
According to Newton’s law of universal gravitation, everything pulls on
everything else with a force that depends upon the masses of the objects and the
distances between their centers of mass.
 The greater the masses, the greater the force is.
 The greater the distance, the smaller is the force.
Gravitation decreases according to the inverse-square law. The force of gravity
weakens as the distance squared.
Earth can be thought of as being surrounded by a gravitational field that
interacts with objects and causes them to experience gravitational forces.
The gravitational field g is equal to the acceleration of a freely falling object.
Objects in orbit around Earth have gravitational force acting on them even they
appear to be weightless.
An Earth satellite is a projectile that moves fast enough tangentially that it falls
around Earth rather than into it.
 The speed of a satellite in a circular orbit is not changed by gravity.
 The speed of a satellite in an elliptical orbit decreases as it recedes from
Earth and increases as it approaches Earth.
According to Einstein’s special theory of relativity, time is affected by motion in
space at constant velocity.
 Time appears to pass more slowly in a frame of reference that is moving
relative to the observer.
All the laws are the same in all uniformly moving frames of reference.