MechanicsIntro & Definitions

Mechanics: studies the motion of objects when subjected

to forces or displacements Kinematics:

studies the motion of objects Dynamics:

studies WHY objects move

Three different types: Rectilinear:

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

A. Train traveling down a straight trackB. A slider on an air-trackC. The valve of a moving bicycle wheelD. A ball rolling off a tableE. Arms moving when a person walksF. A weight oscillating vertically on the end

of a springG. A fly flying around a roomH. Football players running on a field

Classify the type of motion

Trajectory: 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:

Scalar: Quantity described with a magnitude & unit Ex. drove 10 km

Vector: Quantity described with a magnitude, a unit &

a DIRECTION Ex. drove 10km North

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

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.

What is…a) Your displacement?b) Your distance traveled?

6 m west

14 m

4m

10m

Find the displacement for a driver who started at marker +3km and ended at marker -4km.

-5 -4 -3 -2 -1 0 1 2 3 4 5

∆d = d2 – d1

∆d = (-4) – (3)

∆d =-7km