Physics Midterm Vocab

Precision

the degree of exactness of a measurement

Physics

a branch of science that involves the study of the physical world: energy, matter, and how they are related

Accuracy

a description of how well the results of a measurement agree with the accepted value

Motion diagram

a series of images showing the positions of a moving object at regular time intervals

Particle model

a simplified version of a motion diagram in which the moving object is replaced by a series of single points

Position-time graph

a graph that can be used to determine an object's velocity and position, as well as where and when two objects meet, by plotting the time data on a horizontal axis and the position data on a vertical axis

Velocity-time graph

a graph that has velocity plotted on the vertical axis and time plotted on the horizontal axis; its slope is the acceleration of the object whose motion is described by the graph

Average velocity

the ratio of an object's change in position to the time interval during which the change occurred; for uniform motion, it is the slope of the object's position-time graph

Average speed

the distance traveled divided by the time taken to travel that distance; for uniform motion, it is the absolute value of the slope of the object's position-time graph

Distance

the entire length of an object’s path, even if the object moves in many directions

Displacement

a change in position having both magnitude and direction; is equal to the final position minus the initial position

Acceleration

the rate at which the velocity of an object changes

Time interval

the difference between two times

Vector

a quantity that has magnitude and direction

Scalar

a quantity, such as temperature or distance, that is just a number without direction

Magnitude

a measure of size

Force

a push or pull exerted on an object; has both direction and magnitude and may be a contact or a field force

Contact force

a force between two objects in contact

Field force

a force that works without touching anything

Gravity

the force of attraction acting between all objects of matter

Acceleration due to gravity

acceleration caused by gravitational attraction between objects; acceleration on Earth is -9.8 m/s²

Normal force

the perpendicular contact force exerted by a surface on another object

Net force

the vector sum of all the forces on an object

Equilibrium

the condition in which the net force on an object is zero

Tension

the specific name for the force exerted by a rope or a string

Newton’s 1st Law

states that an object at rest will remain at rest and a moving object will continue moving in a straight line with constant speed, if and only if the net force acting on that object is zero

Newton’s 2nd Law

states that the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object being accelerated; f=ma

Newton’s 3rd Law

states that all forces come in pairs and that the two forces in a pair act on different objects and are equal in strength and opposite in direction

Friction

resistive force caused by two surfaces sliding across each other

Free body diagram

a physical model that represents the forces acting on a system

Weight

the gravitational force experienced by an object

Resultant

a vector that represents the sum of two other vectors; it always points from the first vector's tail to the last vector's tip

Measurement

a comparison between an unknown quantity and a standard

Scientific law

a statement about what happens in nature and that seems to be true all the time

Significant digits

the valid digits in a measurement

Mass

the amount of matter in an object

Uniform motion

travel equal distance in equal interval of time - no feeling of motion

Non-uniform motion

travel unequal distance in equal interval of time - feeling of being push or pulled

Kinetic friction

the force exerted on one surface by a second surface when the two surfaces rub against one another because one or both of the surfaces are moving

Static friction

the force exerted on one surface by a second surface when there is no motion between the two surfaces

Coefficient of Kinetic Friction

the slope of a line on a kinetic friction force v. normal force graph. Relates frictional force to normal force and depends on the two surfaces in contact

Coefficient of Static Friction

a dimensionless constant depending on the two surfaces in contact. It is used to calculate the maximum static frictional force that needs to be overcome before motion begins