# Physics Terms

## 60 terms · Physics terms

### fact

a phenomenon about which competent observers who have made a series of observations are in agreement

### Hypothesis

An educated guess; a reasonable explanation of an observation or experimental result that is not fully accepted as factual until tested over and over again by experiment

### Law

A general hypothesis or statement about the relationship of natural quantities that has been tested over and over again and has not been contradicted. Also known as a principle

### Pseudoscience

Fake science that pretends to be real science

### Scientific Method

Principles and procedures for the systematic pursuit of knowledge involving the recognition and formulation of a problem, the collection of data through observation and experiment, and the formulation and testing of hypotheses

### Theory

A synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world

### Newton's first law of motion

Every object continues in its state of rest, or of uniform motion in a straight line, unless compelled to change that state by forces impressed upon it

### Inertia

The property of things to resist changes in motion

### Force

In the simplest sense, a push or a pull.

### Net force

The vector sum of forces that act on an object

### Mechanical Equilibrium

The state of an object or system of objects for which there are not changes in motion. In accord with Newton's first law, if at rest, the state of rest persists. If moving, motion continues without change.

### Equilibrium rule

For any object or system of objects in equilibrium, the sum of the forces acting equals zero.

### Speed

How fast something moves; the distance traveled per unit of time.

### Velocity

The speed of an object and a specification of its direction of motion.

### Vector quantity

Quantity in physics that has both magnitude and direction

### Acceleration

The rate at which velocity changes with time; the change in velocity may be in magnitude, or direction, or both.

### Free Fall

Motion under the influence of gravity only

### Friction

The resistive force that opposes the motion or attempted motion of an object either pass another object with which it is in contact or through a fluid.

### Mass

The quantity of matter in an object. More specifically, it is the measure of the inertia or sluggishness that an object exhibits in response to any effort made to start, stop it, deflect it, or change in any way its state of motion.

### Weight

The force due to gravity on an object

### Kilogram

The fundamental SI unit of mass.

### Newton

The SI unit of force.

### Volume

The quantity of space an object occupies.

### Newton's second law

The acceleration of an object is directly proportional to the net force acting on the object, is in direction of the net force, ans is inversely proportional to the mass of the object.

### Force

Any influence that can cause an object to be accelerated, measured in newtons.

### Free Fall

Motion under the influence of gravitational pull only.

### Terminal speed

The speed at which the acceleration of a falling object terminates because air resistance balances its weight.

### Newton's third law

Whenever one object exerts a force on a second object, the second objects exerts an equal and opposite force on the first.

### Vector quantity

A quantity that has both magnitude and direction.

### Scalar quantity

A quantity that has magnitude but not direction.

### Vector

An arrow drawn to scale used to represent a vector quantity

### Resultant

The net result of a combination of two or more vectors

### Momentum

The product of the mass of an object and its velocity

### Impulse

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

### Relationship of impulse and momentum

Impulse is equal to the change in the momentum of the object that the impulse acts upon.

### 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.

### 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, generated heat, and possibly stick together.

### Work

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

### Power

the time rate of work

### Energy

The property of a system that enables it to do work

### Mechanical energy

Energy due to the position of something or the movement of something

### Potential energy

The energy that something possesses because of its position.

Energy of motion

### Work-energy Theorem

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

### 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, such as a lever or pulley, the increases (or decreases) a force or simply changes the direction of a force

### Lever

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

### Efficiency

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

### Tangential speed

The linear speed tangent to a curved path such as in circular motion.

### Rotational speed

The number of rotations or revolutions per unit of time; often measured in rotations or revolutions per second or per minute.

### Rotational inertia

That property of an object that measures its resistance to any change in its state of rotation; if at rest, the body tends to remain at rest; if rotating, it tends to remain rotating and will continue to do so unless acted upon by an external net torque.

### Torque

The product of force and lever-arm distance, which tends to produce rotation.

### Center of mass

The average position of the mass of an object. The __ moves as if all the external forces acted at this point.

### Center of gravity

The average position of weight or the single point associated with an object where the force of gravity can be considered to act.

### Equilibrium

The state of an object in which it is not acted upon by a net force or a net torque.

### Centripetal force

A force directed toward a fixed point, usually the cause of circular motion.

### Centrifugal force

An outward force apparent in a rotating frame of reference. It is apparent (fictitious) in the sense that it is not part of an interaction but is a result of rotation- with no reaction-force counterpart.

### Angular momentum

The product of a body's rotational inertia and rotational velocity about a particular axis.

### Conservation of angular momentum

When no external torque acts on an object or a system of objects, no change of angular momentum can occur. Hence, the angular momentum before an event involving only internal torques or no torques is equal to the angular momentum after the event.