32 terms

Conceptual Physics 12th e. by Paul G. Hewitt
Summary of Terms, Summary of Formulas, and Terms Within the Textbook

Work

The product of the force and the distance moved by the force.

Power

The time rate of work:

(More generally, power is the rate at which energy is expended.)

(More generally, power is the rate at which energy is expended.)

Energy

The property of a system that enables it to do work.

Potential energy (PE)

The energy that something possesses because of its position.

Kinetic energy (KE)

Energy that something possesses because of its motion.

Work-energy theorem

The work done on an object equals the change in kinetic energy of the object.

Law of Conservation of energy

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.

Machine

A device that increases (or decreases) a force or simply changes the direction of a force.

Conservation of energy for machines

The work output of any machine cannot exceed the work input. In an ideal machine, where no energy is transformed into thermal energy.

Lever

Simple machine consisting of a rigid rod pivoted at a fixed point called the fulcrum.

Efficiency

The percentage of the work put into a machine that is converted into useful work output.

(More generally, useful energy output divided by total energy input.)

(More generally, useful energy output divided by total energy input.)

Joule

The unit of work, also known as a Newton-meter.

Gravitational Potential Energy

The potential energy due to elevated positions.

Ideal Machine

A machine that operates at 100% efficiency. 100% of the work input appears as work ouput.

Impulse

The product of the force acting on an object and the time during which it acts.

Law of Conservation of Momentum

In the absence of an external force, the momentum of a system remains unchanged. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event: *mv (before event) = mv (after event)

Elastic Collision

A collision in which colliding objects rebound without lasting deformation or the generation of heat.

Inelastic Collision

A collision in which the colliding objects become distorted, generate heat, and possibly stick together.

Momentum

Inertia in motion. The product of the mass and the velocity of an object.

Impulse-Momentum Relationship

Impulse is equal to the change in momentum of the object that the impulse acts upon. In symbolic notation:

Ft = ∆ mv

Ft = ∆ mv

∆

A Greek letter often used to denote "change in" or "difference in".

Vector Quanitity

A quantity that has both magnitude and direction.

System

In physics, it may be as tiny as an atom or as large as the universe. We usually refer to it as a the relationship between two objects.

Conserved

The term applied to a physical quantity, such as momentum, energy, or electric charge, that remains unchanged during interactions.

Resultant

The net result of a combination of two or more vectors.

Interaction

Mutual action between objects where each object exerts an equal and opposite force on the other.

We can call one force the *action force* and the other the *reaction force*. Then we can express Newton's third law in the form:

To every action there is always an opposed equal reaction.

System

It may be as tiny as an atom or as large as the universe.

In analyzing changes in motion, Newton's second law reminds us that we must also consider the masses involved. Suppose we let *F* represent both the action and reaction force, *m* the mass of the cannonball, and *M* the mass of the much more massive cannon. The accelerations of the cannonball and the cannon are then found by comparing the ratio of force to mass. The accelerations are:

Cannon ball:

F

---- =**A**

**m**

Cannon:

F

---- = a

**M**

F

---- =

Cannon:

F

---- = a

Lift

In application of Bernoulli's principle, the net upward force produced by the difference between upward and downward pressures. When lift equals weight, horizontal flight is possible.

Component

Mutually perpendicular vectors, usually horizontal and vertical, whose vector sum is a given vector.

Resolution

The process of determining the component of a vector.