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