Mechanics Intro & Definitions

Definitions: Mechanics: Kinematics: Dynamics: studies the motion of objects when subjected to forces or displacements Kinematics: studies the motion of objects Dynamics: studies WHY objects move

Motion: Three different types: Rectilinear: Curvilinear: Random motion along a straight line Ex. sprinter running, sliding cell phone across a table, car traveling down a street Curvilinear: Motion along a curved path Ex. kicked football, car traveling turning a corner Random Combo of rectilinear & curvilinear Ex. skier, hockey player, helicopter

Classify the type of motion Ex: Classify the type of motion Train traveling down a straight track A slider on an air-track The valve of a moving bicycle wheel A ball rolling off a table Arms moving when a person walks A weight oscillating vertically on the end of a spring A fly flying around a room Football players running on a field Rect. Rect. Curv. Curv. Rect. Rect. Random Random

Definitions: Trajectory: Vantage Point: Ex. Baseball Describes the path of an object in motion Vantage Point: Point of view that the path of motion or trajectory is observed from Path of motion or trajectory can “look different” depending on vantage point Ex. Baseball Runner appears differently from the point of view of the pitcher, the 1st baseman, the outfielder, the fans…

Ex. Ball on a moving train From Thrower: From Outside:

Vectors vs Scalar: Scalar: Vector: Quantity described with a magnitude & unit Ex. drove 10 km Vector: Quantity described with a magnitude, a unit & a DIRECTION Ex. drove 10km North

Describing & Calculating Motion: Distance: Distance traveled Scalar quantity d Displacement: Difference between the final & initial position Vector quantity Describes magnitude & direction of change in position ∆d one or two dimensional d = ∆d (ex. 10m) d = 20m BUT ∆d = 10m ∆d = d2 – d1

Ex: You are at your locker. You walk 4m east down the hall. You realize you are going the wrong direction, turn around & walk 10m west. 4m 10m What is… Your displacement? Your distance traveled? 6 m west 14 m

Ex: ∆d = d2 – d1 ∆d = (-4) – (3) ∆d =-7km Find the displacement for a driver who started at marker +3km and ended at marker -4km. -5 -4 -3 -2 -1 1 2 3 4 5 ∆d = d2 – d1 ∆d = (-4) – (3) ∆d =-7km

Try: pg 166 #1 - 6 pg 170 #1 - 3