Motion in One Direction Chapter 2 Goals: motion, displacement, velocity, acceleration, freefall, acceleration due to gravity and equations to solve for velocity, acceleration and displacement

Section 2.1 Displacement and velocity Distance- space between two points, one dimension, length, measured in meters (scalar) Total change in position Distance- space between two points, one dimension, length, measured in meters (scalar) Total change in position Displacement- space between two points in one direction, length, meters, pos or neg (vector) Net change in position ΔX= X f – X i

Velocity  Velocity- rate of displacement speed?  rates occur in a unit of time seconds  velocity = displacement / time  v = ΔX / t m/s  Graph time on X and position on Y  Instantaneous velocity is a point on a graph  Average is the total displacement per unit of time  Graph Velocities pos (upward curve), stationary (horizontal curve), neg (downward curve)

Section 2.2 Acceleration  What is any change in velocity?  Acceleration- rate of change in velocity  change in velocity per unit of time  a = Δv / t = v f – v i/ t  m / s 2  positive or negative  average acceleration = v f + v i/ 2 v = Δx / t Δx = ½ (vf + vi) t

 Graphing acceleration time on x and velocity on y  pos (upward slope), constant velocity (horizontal curve), neg (downward curve)  What if you had……………………………..  pos v and pos a ?  right! object is speeding up  pos v and neg a ?  right! object is slowing down  neg v and neg a ?  right! object is speeding up  neg v and pos a ?  right! Object is slowing down  what about 0 v and 0 a ?  the object is still  what about 0 a ?  the object has constant velocity (like terminal v)

Section 2.3 Free Fall  Why do objects fall? Accelerate towards Earth  Remember: acceleration is a rate of change in Velocity due to an unbalanced force  Unbalanced forces cause accelerations  Gravity and Air Friction are the unbalanced forces  Gravity is a force of attraction accelerating all objects in freefall towards Earth  acceleration due to gravity is a constant and known to be m/s 2 g= 9.81 m/s 2  use little “g” for “a” in problems involving freefall

In conclusion:  we considered the following variables:  x v a g  Δx for change in displacement x f - x i  Δt for change in time t f - t i  a for acceleration Δv/Δt  we also considered average velocity v f + v i / 2 so we can calculate average acceleration in m/s 2  and derived equations for calculating displacement Δx=1/2 (v f +v i ) t if you are given “v” and “t” or Δx=v i Δt + 1/2a(t) 2 if you are given acceleration and time

 or if you want to find velocity which is: v=a times t use these derivatives: v f = v i + a (t) or v f 2 =v i a Δx

 Question  What is so great about Physics?  Answer  Physics is ACCELERATING!