- air resistance
- a frictional force that slows the motion of objects as they travel through the air; when solving basic physics problems, air resistance is assumed to be zero

- amplitude
- the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position

- analytical method
- the method of determining the magnitude and direction of a resultant vector using the Pythagorean theorem and trigonometric identities

- component (of a 2-dimensional vector)
- a piece of a vector that points in a particular direction, usually in the direction of one of the axes of a chosen coordinate system; every 2-d vector can be expressed as a sum of two perpendicular vector components

- deformation
- displacement from equilibrium, or change in shape due to the application of force

- equilibrium position
- where an object would naturally rest in the absence of a net force

- frequency
- number of events per unit of time

- graphical method
- drawing vectors on a graph to add them using the head-to-tail method

- head (of a vector)
- the end point of a vector; the location of the vector’s arrow; also referred to as the tip

- head-to-tail method
- a method of adding vectors in which the tail of each vector is placed at the head of the previous vector

- Hooke’s law
- proportional relationship between the force
**F**on a material and the deformation $\Delta L$ it causes, $F=k\Delta L$

- kinetic friction
- a force that opposes the motion of two systems that are in contact and moving relative to one another

- maximum height (of a projectile)
- the highest altitude, or maximum displacement in the vertical position reached in the path of a projectile

- oscillate
- moving back and forth regularly between two points

- period
- time it takes to complete one oscillation

- periodic motion
- motion that repeats itself at regular time intervals

- projectile
- an object that travels through the air and experiences only acceleration due to gravity

- projectile motion
- the motion of an object that is subject only to the acceleration of gravity

- range
- the maximum horizontal distance that a projectile travels

- restoring force
- force acting in opposition to the force causing the deformation

- resultant
- the sum of the a collection of vectors

- resultant vector
- the vector sum of two or more vectors

- simple harmonic motion
- the oscillatory motion in a system where the net force can be described by Hooke’s law

- simple pendulum
- an object with a small mass suspended from a light wire or string

- static friction
- a force that prevents the relative motion of two systems that are in contact and are not moving relative to one another

- tail
- the starting point of a vector; the point opposite to the head or tip of the arrow

- trajectory
- the path of a projectile through the air

- vector addition
- adding together two or more vectors